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Drop SANE Standard version 2 draft documentation. Re #35 

This removes revisions 0.05, 0.06, 0.07 and 0.08 as well as their
exports to various formats.  Note that revisions 0.05 and 0.06 were
never added to version control.
merge-requests/4/merge
Olaf Meeuwissen 2020-03-08 13:07:09 +09:00
rodzic 6fb482673c
commit 32dfd7c86e
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<html><body>
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<img src=../icons/up_gr.gif border=2 alt="Previous"></a>
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<a href="doc000.html"><img src=../icons/contents.gif alt="Contents"></a>
<a href="doc019.html"><img src=../icons/index.gif alt="Index"></a>
<hr>
<title>Contents</title>
<h1>Contents</h1><p>
<table>
<tr></tr><tr><td colspan=20>1<tt> </tt><a href="doc002.html#s1"><b>Preface</b></a></td></tr>
<tr><td></td><td colspan=20>1.1<tt> </tt><a href="doc003.html#s1.1">About This Document</a></td></tr>
<tr><td></td><td></td><td colspan=20>1.1.1<tt> </tt><a href="doc003.html#s1.1.1">Typographic Conventions</a></td></tr>
<tr></tr><tr><td colspan=20>2<tt> </tt><a href="doc004.html#s2"><b>Introduction</b></a></td></tr>
<tr><td></td><td colspan=20>2.1<tt> </tt><a href="doc005.html#s2.1">Terminology</a></td></tr>
<tr></tr><tr><td colspan=20>3<tt> </tt><a href="doc006.html#s3"><b>The SANE Environment</b></a></td></tr>
<tr><td></td><td colspan=20>3.1<tt> </tt><a href="doc007.html#s3.1">Attaching to a SANE backend</a></td></tr>
<tr><td></td><td colspan=20>3.2<tt> </tt><a href="doc008.html#s3.2">Image Data Format</a></td></tr>
<tr><td></td><td></td><td colspan=20>3.2.1<tt> </tt><a href="doc008.html#s3.2.1">Pixel oriented frames</a></td></tr>
<tr><td></td><td></td><td colspan=20>3.2.2<tt> </tt><a href="doc008.html#s3.2.2">Arbitrary data frames</a></td></tr>
<tr></tr><tr><td colspan=20>4<tt> </tt><a href="doc009.html#s4"><b>The SANE Application Programmer Interface (API)</b></a></td></tr>
<tr><td></td><td colspan=20>4.1<tt> </tt><a href="doc010.html#s4.1">Version Control</a></td></tr>
<tr><td></td><td colspan=20>4.2<tt> </tt><a href="doc011.html#s4.2">Data Types</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.1<tt> </tt><a href="doc011.html#s4.2.1">Base Types</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.2<tt> </tt><a href="doc011.html#s4.2.2">Boolean Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.3<tt> </tt><a href="doc011.html#s4.2.3">Integer Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.4<tt> </tt><a href="doc011.html#s4.2.4">Fixed-point Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.5<tt> </tt><a href="doc011.html#s4.2.5">Text</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.5.1<tt> </tt><a href="doc011.html#s4.2.5.1">Character Type</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.5.2<tt> </tt><a href="doc011.html#s4.2.5.2">String Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.6<tt> </tt><a href="doc011.html#s4.2.6">Scanner Handle Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.7<tt> </tt><a href="doc011.html#s4.2.7">Status Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.8<tt> </tt><a href="doc011.html#s4.2.8">Device Descriptor Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.9<tt> </tt><a href="doc011.html#s4.2.9">Option Descriptor Type</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.1<tt> </tt><a href="doc011.html#s4.2.9.1">Option Name</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.2<tt> </tt><a href="doc011.html#s4.2.9.2">Option Title</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.3<tt> </tt><a href="doc011.html#s4.2.9.3">Option Description</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.4<tt> </tt><a href="doc011.html#s4.2.9.4">Option Value Type</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.5<tt> </tt><a href="doc011.html#s4.2.9.5">Option Value Unit</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.6<tt> </tt><a href="doc011.html#s4.2.9.6">Option Value Size</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.7<tt> </tt><a href="doc011.html#s4.2.9.7">Option Capabilities</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.8<tt> </tt><a href="doc011.html#s4.2.9.8">Option Value Constraints</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.10<tt> </tt><a href="doc011.html#s4.2.10">Internationalization</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.10.1<tt> </tt><a href="doc011.html#s4.2.10.1">How is a text marked for translation</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.10.2<tt> </tt><a href="doc011.html#s4.2.10.2">Which texts shall be marked for translation?</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.10.3<tt> </tt><a href="doc011.html#s4.2.10.3">File formats and translation functions</a></td></tr>
<tr><td></td><td colspan=20>4.3<tt> </tt><a href="doc012.html#s4.3">Operations</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.1<tt> </tt><a href="doc012.html#s4.3.1"><tt>sane_init</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.2<tt> </tt><a href="doc012.html#s4.3.2"><tt>sane_exit</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.3<tt> </tt><a href="doc012.html#s4.3.3"><tt>sane_get_devices</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.4<tt> </tt><a href="doc012.html#s4.3.4"><tt>sane_open</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.5<tt> </tt><a href="doc012.html#s4.3.5"><tt>sane_close</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.6<tt> </tt><a href="doc012.html#s4.3.6"><tt>sane_get_option_descriptor</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.7<tt> </tt><a href="doc012.html#s4.3.7"><tt>sane_control_option</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.8<tt> </tt><a href="doc012.html#s4.3.8"><tt>sane_get_parameters</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.9<tt> </tt><a href="doc012.html#s4.3.9"><tt>sane_start</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.10<tt> </tt><a href="doc012.html#s4.3.10"><tt>sane_read</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.11<tt> </tt><a href="doc012.html#s4.3.11"><tt>sane_cancel</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.12<tt> </tt><a href="doc012.html#s4.3.12"><tt>sane_set_io_mode</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.13<tt> </tt><a href="doc012.html#s4.3.13"><tt>sane_get_select_fd</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.14<tt> </tt><a href="doc012.html#s4.3.14"><tt>sane_strstatus</tt></a></td></tr>
<tr><td></td><td colspan=20>4.4<tt> </tt><a href="doc013.html#s4.4">Code Flow</a></td></tr>
<tr><td></td><td colspan=20>4.5<tt> </tt><a href="doc014.html#s4.5">Well-Known Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.1<tt> </tt><a href="doc014.html#s4.5.1">Option Number Count</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.2<tt> </tt><a href="doc014.html#s4.5.2">Scan Resolution Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.3<tt> </tt><a href="doc014.html#s4.5.3">Preview Mode Option</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.4<tt> </tt><a href="doc014.html#s4.5.4">Scan Area Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.5<tt> </tt><a href="doc014.html#s4.5.5">Depth option</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.6<tt> </tt><a href="doc014.html#s4.5.6">Gamma table options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.7<tt> </tt><a href="doc014.html#s4.5.7">Scan Mode options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.8<tt> </tt><a href="doc014.html#s4.5.8">Scan Source options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.9<tt> </tt><a href="doc014.html#s4.5.9">Threshold</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.10<tt> </tt><a href="doc014.html#s4.5.10">Analog gamma</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.11<tt> </tt><a href="doc014.html#s4.5.11">Shadow</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.12<tt> </tt><a href="doc014.html#s4.5.12">Highlight</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.13<tt> </tt><a href="doc014.html#s4.5.13">Turn lamp on and off</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.14<tt> </tt><a href="doc014.html#s4.5.14">Scanner buttons</a></td></tr>
<tr></tr><tr><td colspan=20>5<tt> </tt><a href="doc015.html#s5"><b>Network Protocol</b></a></td></tr>
<tr><td></td><td colspan=20>5.1<tt> </tt><a href="doc016.html#s5.1">Data Type Encoding</a></td></tr>
<tr><td></td><td></td><td colspan=20>5.1.1<tt> </tt><a href="doc016.html#s5.1.1">Primitive Data Types</a></td></tr>
<tr><td></td><td></td><td colspan=20>5.1.2<tt> </tt><a href="doc016.html#s5.1.2">Type Constructors</a></td></tr>
<tr><td></td><td colspan=20>5.2<tt> </tt><a href="doc017.html#s5.2">Remote Procedure Call Requests</a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.1<tt> </tt><a href="doc017.html#s5.2.1"><tt>SANE_NET_INIT<a name="i146"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.2<tt> </tt><a href="doc017.html#s5.2.2"><tt>SANE_NET_GET_DEVICES<a name="i148"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.3<tt> </tt><a href="doc017.html#s5.2.3"><tt>SANE_NET_OPEN<a name="i150"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.4<tt> </tt><a href="doc017.html#s5.2.4"><tt>SANE_NET_CLOSE<a name="i152"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.5<tt> </tt><a href="doc017.html#s5.2.5"><tt>SANE_NET_GET_OPTION_DESCRIPTORS<a name="i154"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.6<tt> </tt><a href="doc017.html#s5.2.6"><tt>SANE_NET_CONTROL_OPTION<a name="i157"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.7<tt> </tt><a href="doc017.html#s5.2.7"><tt>SANE_NET_GET_PARAMETERS<a name="i159"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.8<tt> </tt><a href="doc017.html#s5.2.8"><tt>SANE_NET_START<a name="i161"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.9<tt> </tt><a href="doc017.html#s5.2.9"><tt>SANE_NET_CANCEL<a name="i163"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.10<tt> </tt><a href="doc017.html#s5.2.10"><tt>SANE_NET_AUTHORIZE<a name="i165"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.11<tt> </tt><a href="doc017.html#s5.2.11"><tt>SANE_NET_EXIT<a name="i168"></tt></a></td></tr>
<tr></tr><tr><td colspan=20>6<tt> </tt><a href="doc018.html#s6"><b>Contact Information</b></a></td></tr>
</table>
<h1>List of Figures</h1>
<table>
<tr><td>1</td><td><a href="doc007.html#f1">Example SANE Hiearchy</a></td></tr>
<tr><td>2</td><td><a href="doc008.html#f2">Transfer order of image data bytes</a></td></tr>
<tr><td>3</td><td><a href="doc008.html#f3">Bit and byte order of image data</a></td></tr>
<tr><td>4</td><td><a href="doc013.html#f4">Code flow</a></td></tr>
<tr><td>5</td><td><a href="doc014.html#f5">Scan area options</a></td></tr>
</table>
<h1>List of Tables</h1>
<table>
<tr><td>1</td><td><a href="doc011.html#f1">Status Codes</a></td></tr>
<tr><td>2</td><td><a href="doc011.html#f2">Predefined Device Information Strings</a></td></tr>
<tr><td>3</td><td><a href="doc011.html#f3">Option Value Types (<tt>SANE_Value_Type</tt>)</a></td></tr>
<tr><td>4</td><td><a href="doc011.html#f4">Physical Units (<tt>SANE_Unit</tt>)</a></td></tr>
<tr><td>5</td><td><a href="doc011.html#f5">Option Capabilities</a></td></tr>
<tr><td>6</td><td><a href="doc011.html#f6">Option Value Constraints</a></td></tr>
<tr><td>7</td><td><a href="doc012.html#f7">Action Values (<tt>SANE_Action</tt>)</a></td></tr>
<tr><td>8</td><td><a href="doc012.html#f8">Additional Information Returned When Setting an Option</a></td></tr>
<tr><td>9</td><td><a href="doc012.html#f9">Frame Format (<tt>SANE_Frame</tt>)</a></td></tr>
</table>
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<title>./sane</title>
<p>
<p>
<p>
<p>
<p>
<p>
<p>
<p><center><h1><font size=+4>SANE Standard Version 2.0 proposal 0.07 - rauch/beck</font></h1></center>
<center></center>
<center>Dec 5, 2002</center>
<p>
<p><h1><a href="doc002.html">1 Preface</a></h1><h1><a href="doc004.html">2 Introduction</a></h1><h1><a href="doc006.html">3 The SANE Environment</a></h1><h1><a href="doc009.html">4 The SANE Application Programmer Interface (API)</a></h1><h1><a href="doc015.html">5 Network Protocol</a></h1><h1><a href="doc018.html">6 Contact Information</a></h1><p><hr>
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<hr>
<title>Preface</title>
<h1><a name="s1">1 Preface</a></h1>
<p>The SANE standard is being developed by a group of free-software
developers. The process is open to the public and comments as well as
suggestions for improvements are welcome. Information on how to join
the SANE development process can be found in Chapter
<a href="doc018.html#s6">6</a>.
<p>The SANE standard is intended to streamline software development by
providing a standard application programming interface to access
raster scanner hardware. This should reduce the number of different
driver implementations, thereby reducing the need for reimplementing
similar code.
<p><h2><a href="doc003.html">1.1 About This Document</a></h2><p><hr>
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<hr>
<title>About This Document</title>
<h2><a name="s1.1">1.1 About This Document</a></h2>
<p>This document is intended for developers who are creating either an
application that requires access to raster scanner hardware and for
developers who are implementing a SANE driver. It does not cover
specific implementations of SANE components. Its sole purpose is to
describe and define the SANE application interface that will enable
any application on any platform to interoperate with any SANE backend
for that platform.
<p>The remainder of this document is organized as follows.
Chapter <a href="doc004.html#s2">2</a> provides introductional material.
Chapter <a href="doc006.html#s3">3</a> presents the environment SANE is designed
for. Chapter <a href="doc009.html#s4">4</a> details the SANE Application Programmer
Interface. Chapter <a href="doc015.html#s5">5</a> specifies the network protocol that
can be used to implement the SANE API in a network transparent
fashion. Finally, Chapter <a href="doc018.html#s6">6</a> gives information on how
to join the SANE development process.
<p><h3><a name="s1.1.1">1.1.1 Typographic Conventions</a></h3>
<p>Changes since the last revision of this document are highlighted
like this:
<p><font color="darkgreen">
Paragraphs that changed since the last revision of the documention
are marked like this paragraph.
</font>
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<title>Introduction</title>
<h1><a name="s2">2 Introduction</a></h1>
<p>SANE is an application programming interface (API) that provides
standardized access to any raster image scanner hardware. The
standardized interface allows to write just one driver for each
scanner device instead of one driver for each scanner and application.
The reduction in the number of required drivers provides significant
savings in development time. More importantly, SANE raises the level
at which applications can work. As such, it will enable applications
that were previously unheard of in the UNIX world. While SANE is
primarily targeted at a UNIX environment, the standard has been
carefully designed to make it possible to implement the API on
virtually any hardware or operating system.
<p>SANE is an acronym for ``Scanner Access Now Easy.'' Also, the hope is
that SANE is sane in the sense that it will allow easy implementation
of the API while accommodating all features required by today's
scanner hardware and applications. Specifically, SANE should be broad
enough to accommodate devices such as scanners, digital still and
video cameras, as well as virtual devices like image file filters.
<p><h2><a href="doc005.html">2.1 Terminology</a></h2><p><hr>
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<title>Terminology</title>
<h2><a name="s2.1">2.1 Terminology</a></h2>
<p>An application that uses the SANE interface is called a SANE <em>
frontend</em>. A driver that implements the SANE interface is called a
SANE <em>backend</em>. A <em>meta backend</em> provides some means to
manage one or more other backends.
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<title>The SANE Environment</title>
<h1><a name="s3">3 The SANE Environment</a></h1>
<p>SANE is defined as a C-callable library interface. Accessing a raster
scanner device typically consists of two phases: first, various
controls of the scanner need to be setup or queried. In the second
phase, one or more images are acquired.
<p>Since the device controls are widely different from device to device,
SANE provides a generic interface that makes it easy for a frontend to
give a user access to all controls without having to understand each
and every device control. The design principle used here is to
abstract each device control into a SANE <em>option</em>. An option is
a self-describing name/value pair. For example, the brightness
control of a camera might be represented by an option called
<tt>brightness</tt> whose value is an integer in the range from 0 to
255.
<p>With self-describing options, a backend need not be concerned with
<em>presentation</em> issues: the backend simply provides a list of
options that describe all the controls available in the device.
Similarly, there are benefits to the frontend: it need not be
concerned with the <em>meaning</em> of each option. It simply provides
means to present and alter the options defined by the backend.
<p><h2><a href="doc007.html">3.1 Attaching to a SANE backend</a></h2><h2><a href="doc008.html">3.2 Image Data Format</a></h2><p><hr>
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<title>Attaching to a SANE backend</title>
<h2><a name="s3.1">3.1 Attaching to a SANE backend</a></h2>
<p>The process through which a SANE frontend connects to a backend is
platform dependent. Several possibilities exist:
<ul>
<p><li><b>Static linking:</b> A SANE backend may be linked directly into
a frontend. While the simplest method of attaching to a backend, it
is somewhat limited in functionality since the available devices is
limited to the ones for which support has been linked in when the
frontend was built. But even so static linking can be quite useful,
particularly when combined with a backend that can access scanners
via a network. Also, it is possible to support multiple backends
simultaneously by implementing a meta backend that manages several
backends that have been compiled in such a manner that they export
unique function names. For example, a backend called <tt>be</tt>
would normally export a function called <tt>sane_read()</tt>. If
each backend would provide such a function, static linking would
fail due to multiple conflicting definitions of the same symbol.
This can be resolved by having backend <tt>be</tt> include a
header file that has lines of the form:
<blockquote>
<pre>
#define sane_read be_sane_read
</pre>
</blockquote>
With definitions of this kind, backend <tt>be</tt> will export
function name <tt>be_sane_read()</tt>. Thus, all backends will
export unique names. As long as a meta backend knows about these
names, it is possible to combine several backends at link time and
select and use them dynamically at runtime.
<p><li><b>Dynamic linking:</b> A simpler yet more powerful way to
support multiple backends is to exploit dynamic linking on platforms
that support it. In this case, a frontend is linked against a
shared library that implements any SANE backend. Since each
dynamically linked backend exports the same set of global symbols
(all starting with the prefix <tt>sane_</tt>), the dynamic library
that gets loaded at runtime does not necessarily have to be the same
one as one the frontend got linked against. In other words, it is
possible to switch the backend by installing the appropriate backend
dynamic library.
<p> More importantly, dynamic linking makes it easy to implement a meta
backend that loads other backends <em>on demand</em>. This is a
powerful mechanism since it allows adding new backends merely by
installing a shared library and updating a configuration file.
<p><li><b>Network connection:</b> Arguably the ultimate way to attach to
a scanner is by using the network to connect to a backend on a
remote machine. This makes it possible to scan images from any host
in the universe, as long as there is a network connection to that
host and provided the user is permitted to access that scanner.
<p></ul>
<p><p><a name="f1"></a>
<center>
<img width=780 height=384 src="img000.gif">
<p><center>Figure 1: Example SANE Hiearchy</center>
</center>
<p>
<p>The above discussion lists just a few ways for frontends to attach to
a backend. It is of course possible to combine these solutions to
provide an entire hierarchy of SANE backends. Such a hierarchy is
depicted in Figure <a href="doc007.html#f1">1</a>. The figure shows that machine
A uses a dynamic-linking based meta backend called <tt>dll</tt> to
access the backends called <tt>pnm</tt>, <tt>mustek</tt>, and <tt>net</tt>.
The first two are real backends, whereas the last one is a meta
backend that provides network transparent access to remote scanners.
In the figure, machine B provides non-local access to its scanners
through the SANE frontend called <tt>saned</tt>. The <tt>saned</tt> in
turn has access to the <tt>hp</tt> and <tt>autolum</tt> backends through
another instance of the <tt>dll</tt> backend. The <tt>autolum</tt> meta
backend is used to automatically adjust the luminance (brightness) of
the image data acquired by the camera backend called <tt>qcam</tt>.
<p>Note that a meta backend really is both a frontend and a backend at
the same time. It is a frontend from the viewpoint of the backends
that it manages and a backend from the viewpoint of the frontends that
access it. The name ``meta backend'' was chosen primarily because the
SANE standard describes the interface from the viewpoint of a (real)
frontend.
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<title>Image Data Format</title>
<h2><a name="s3.2">3.2 Image Data Format</a></h2><a name="i0">
<p>Arguably the most important aspect of an image acquisition system is how
images are represented. The SANE approach is to define a simple yet powerful
representation that is sufficient for vast majority of applications and
devices. While the representation is simple, the interface has been defined
carefully to allow extending it in the future without breaking backwards
compatibility. Thus, it will be possible to accommodate future applications or
devices that were not anticipated at the time this standard was created.
<p>A SANE image is a rectangular area. The rectangular area is subdivided into a
number of rows and columns. At the intersection of each row and column is a
(preferable quadratic) pixel. A pixel consists of one or more sample values.
Each sample value represents one channel (e.g., the red channel).
<p>The SANE API transmits an image as a sequence of frames. Each frame covers
the same rectangular area as the entire image, but may contain only a subset
of the channels in the final image. For example, a red/green/blue image could
either be transmitted as a single frame that contains the sample values for
all three channels or it could be transmitted as a sequence of three frames:
the first frame containing the red channel, the second the green channel, and
the third the blue channel.
<p>When transmitting an image frame by frame, the frontend needs to know what
part of the image a frame represents (and how many frames it should expect).
For that purpose, the SANE API tags every frame with a type and a format
descriptor.
<p><font color="darkgreen">
There are two different types of frames: pixel oriented frames
<tt>SANE_FRAME_RAW<a name="i1"></tt> and arbitrary data frames
<tt>SANE_FRAME_MIME<a name="i2"></tt>. These types are discussed in detail in the
following sections. The frame types used by version 1 of this standard
(<tt>SANE_FRAME_GRAY<a name="i3"></tt>, <tt>SANE_FRAME_RGB<a name="i4"></tt>,
<tt>SANE_FRAME_RED<a name="i5"></tt>, <tt>SANE_FRAME_GREEN<a name="i6"></tt>, and
<tt>SANE_FRAME_BLUE<a name="i7"></tt>) are obsolete and superseded by
<tt>SANE_FRAME_RAW<a name="i8"></tt>.
<p> <h3><a name="s3.2.1">3.2.1 Pixel oriented frames</a></h3>
<p> The type of pixel oriented frames is <tt>SANE_FRAME_RAW<a name="i9"></tt>. The
frame contains one or more channels of data in a channel-interleaved format,
that represents sample values from a property of the individual pixels that
is subject to further description in the <tt>format_desc</tt> member of the
<tt>SANE_Parameters</tt> structured type. See section <a href="doc012.html#s4.3.8">4.3.8</a>
on page <a href="doc012.html#s4.3.8">4.3.8</a> for details about the format
descriptions.
</font>
<p> Each sample value has a certain bit depth. The bit depth is fixed for the
entire image and can be as small as one bit. Valid bit depths are 1, 8, or
16 bits per sample. If a device's natural bit depth is something else, it is
up to the driver to scale the sample values appropriately (e.g., a 4 bit
sample could be scaled by a factor of four to represent a sample value of
depth 8).
<p><font color="darkgreen">
The complete image may consist of several different channels. The number of channels
is defined by member <tt>channels_per_image</tt> of <tt>SANE_Parameters</tt>.
The image may be transmitted in an arbitary number of frames which can be
determined by watching the <tt>SANE_PFLAG_LAST_FRAME</tt> flag in said type (or by
counting the channels). Note: This frame type replaces all frame types of
the SANE standard version 1.
</font>
<p>Conceptually, each pixel oriented frame is transmitted a byte at a time. Each
byte may contain 8 sample values (for an image bit depth of 1), one full
sample value (for an image bit depth of 8), or a partial sample value (for an
image bit depth of 16 or bigger). In the latter case, the bytes of each
sample value are transmitted in the machine's native byte order.
<blockquote>
<center>
<b>Backend Implementation Note</b>
</center>
A network-based meta backend will have to ensure that the byte order
in image data is adjusted appropriately if necessary. For example,
when the meta backend attaches to the server proxy, the proxy may
inform the backend of the server's byte order. The backend can then
apply the adjustment if necessary. In essence, this implements a
``receiver-makes-right'' approach.
</blockquote>
<p><p><a name="f2"></a>
<center>
<img width=390 height=196 src="img001.gif">
<p><center>Figure 2: Transfer order of image data bytes</center>
</center>
<p>
<p>The order in which the sample values in a frame are transmitted is illustrated
in Figure <a href="doc008.html#f2">2</a>. As can be seen, the values are transmitted row by
row and each row is transmitted from left-most to right-most column. The
left-to-right, top-to-bottom transmission order applies when the image is
viewed in its normal orientation (as it would be displayed on a screen, for
example).
<p>If a frame contains multiple channels, then the channels are transmitted in an
interleaved fashion. Figure <a href="doc008.html#f3">3</a> illustrates this for the case
where a frame contains a complete red/green/blue image with a bit-depth of 8.
<p><p><a name="f3"></a>
<center>
<img width=624 height=111 src="img002.gif">
<p><center>Figure 3: Bit and byte order of image data</center>
</center>
<p>
<p>For a bit depth of 1, each byte contains 8 sample values of a <em>single</em>
channel. In other words, a bit depth 1 frame is transmitted in a byte
interleaved fashion. The first sample of each byte is represented by the most
significant bit.
<p><font color="darkgreen">
For gray channels at a bit depth of 1 only two sample values are possible: 1
represents minimum intensity (black) and 0 represents maximum intensity
(white). For all other channel types and bit depths a sample value of 0
represents minimum intensity and larger values represent increasing intensity.
<p><h3><a name="s3.2.2">3.2.2 Arbitrary data frames</a></h3>
<p>It also is possible to transmit arbitrary (not necessaryly pixel oriented)
data. This allows transmission of compressed images like jpeg, tiff, etc.
<p>The type of arbitrary data frames is <tt>SANE_FRAME_MIME<a name="i10"></tt>.
The frame contains arbitrary data of the MIME (see RFC 1521/1522) type that is
given in the <tt>format_desc</tt> member of the <tt>SANE_Parameters</tt>
structured type (see See section <a href="doc012.html#s4.3.8">4.3.8</a> on
page <a href="doc012.html#s4.3.8">4.3.8</a>). As such, it is assumed to be
incomprehensible to the frontend, except for selected types the frontend is
specifically capable of handling internally. The frontend is free to ignore
those frames, or employ any appropriate means to otherwise handle this data
(like saving them to disk or spawning an external viewer).
</font>
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<title>The SANE Application Programmer Interface (API)</title>
<h1><a name="s4">4 The SANE Application Programmer Interface (API)</a></h1>
<p><font color="darkgreen">
This Section defines version 2 of the SANE application
programmer interface (API). Any SANE frontend must depend on the
interface defined in this section only. Converseley, any SANE backend
must implement its functionality in accordance with this
specification. The interface as documented here is declared as a C
callable interface in a file called <tt>sane/sane-2.h</tt>. This file should
normally be included via a C pre-processor directive of the form:
<pre>
#include &lt;sane/sane-2.h&gt;
</pre>
</font>
<p><h2><a href="doc010.html">4.1 Version Control</a></h2><h2><a href="doc011.html">4.2 Data Types</a></h2><h2><a href="doc012.html">4.3 Operations</a></h2><h2><a href="doc013.html">4.4 Code Flow</a></h2><h2><a href="doc014.html">4.5 Well-Known Options</a></h2><p><hr>
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<title>Version Control</title>
<h2><a name="s4.1">4.1 Version Control</a></h2>
<p>The SANE standard is expected to evolve over time. Whenever a change
to the SANE standard is made that may render an existing frontend or
backend incompatible with the new standard, the major version number
must be increased. Thus, any frontend/backend pair is compatible
provided the major version number of the SANE standard they implement
is the same. A frontend may implement backwards compatiblity by
allowing major numbers that are smaller than the expected major number
(provided the frontend really can cope with the older version). In
contrast, a backend always provides support for one and only one
version of the standard. If a specific application does require that
two different versions of the same backend are accessible at the same
time, it is possible to do so by installing the two versions under
different names.
<p>SANE version control also includes a minor version number and a build
revision. While control of these numbers remains with the implementor
of a backend, the recommended use is as follows. The minor version is
incremented with each official release of a backend. The build
revision is increased with each build of a backend.
<p>The SANE API provides the following five macros to manage version
numbers.
<blockquote>
<dl>
<dt><tt>SANE_CURRENT_MAJOR<a name="i11"></tt>:<dd> The value of this macro is the
number of the SANE standard that the interface implements.
<p> <dt><tt>SANE_VERSION_CODE<a name="i12">(<i>maj</i>,<i>min</i>,<i>bld</i>)</tt>:<dd>
This macro can be used to build a monotonically increasing version
code. A SANE version code consists of the SANE standard major
version number (<i>maj</i>), the minor version number <i>min</i>,
and the build revision of a backend (<i>bld</i>). The major and
minor version numbers must be in the range 0...255 and the
build revision must be in the range 0...65535.
<p> Version codes are monotonic in the sense that it is possible to
apply relational operators (e.g., equality or less-than test)
directly on the version code rather than individually on the three
components of the version code.
<p> Note that the major version number alone determines whether a
frontend/backend pair is compatible. The minor version and the
build revision are used for informational and bug-fixing purposes
only.
<dt><tt>SANE_VERSION_MAJOR<a name="i13">(<i>vc</i>)</tt>:<dd> This macro returns the
major version number component of the version code passed in
argument <i>vc</i>.
<dt><tt>SANE_VERSION_MINOR(<i>vc</i>)</tt>:<dd> This macro returns the
minor version number component of the version code passed in
argument <i>vc</i>.
<dt><tt>SANE_VERSION_BUILD(<i>vc</i>)</tt>:<dd> This macro returns the
build revision component of the version code passed in argument
<i>vc</i>.
</dl>
</blockquote>
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<title>Operations</title>
<h2><a name="s4.3">4.3 Operations</a></h2>
<p><h3><a name="s4.3.1">4.3.1 <tt>sane_init</tt></a></h3>
<p>This function must be called before any other SANE function can be called.
The behavior of a SANE backend is undefined if this function is not called
first or if the status code returned by <tt>sane_init</tt> is different from
<tt>SANE_STATUS_GOOD<a name="i77"></tt>. The version code of the backend is returned
in the value pointed to by <tt>version_code</tt>. If that pointer is
<tt>NULL</tt>, no version code is returned. Argument <tt>authorize</tt> is either
a pointer to a function that is invoked when the backend requires
authentication for a specific resource or <tt>NULL</tt> if the frontend does not
support authentication.
<blockquote><a name="i78">
<pre>
SANE_Status sane_init (SANE_Int * version_code,
SANE_Authorization_Callback authorize);
</pre>
</blockquote>
<p>The authorization function may be called by a backend in response to
any of the following calls:
<blockquote>
<tt>sane_open</tt>, <tt>sane_control_option</tt>, <tt>sane_start</tt>
</blockquote>
If a backend was initialized without authorization function, then
authorization requests that cannot be handled by the backend itself
will fail automatically and the user may be prevented from accessing
protected resources. Backends are encouraged to implement means of
authentication that do not require user assistance. E.g., on a
multi-user system that authenticates users through a login process a
backend could automatically lookup the apporpriate password based on
resource- and user-name.
<p>The authentication function type has the following declaration:
<blockquote><a name="i79">
<a name="i80"><a name="i81"><a name="i82">
<pre>
#define SANE_MAX_USERNAME_LEN 128
#define SANE_MAX_PASSWORD_LEN 128
typedef void (*SANE_Authorization_Callback)
(SANE_String_Const resource,
SANE_Char username[SANE_MAX_USERNAME_LEN],
SANE_Char password[SANE_MAX_PASSWORD_LEN]);
</pre>
</blockquote>
Three arguments are passed to the authorization function:
<tt>resource</tt> is a string specifying the name of the resource that
requires authorization. A frontend should use this string to build a
user-prompt requesting a username and a password. The <tt>username</tt>
and <tt>password</tt> arguments are (pointers to) an array of
<tt>SANE_MAX_USERNAME_LEN</tt> and <tt>SANE_MAX_PASSWORD_LEN</tt>
characters, respectively. The authorization call should place the
entered username and password in these arrays. The returned strings
<em>must</em> be ASCII-NUL terminated.
<p><h3><a name="s4.3.2">4.3.2 <tt>sane_exit</tt></a></h3>
<p>This function must be called to terminate use of a backend. The
function will first close all device handles that still might be open
(it is recommended to close device handles explicitly through a call
to <tt>sane_close()</tt>, but backends are required to release all
resources upon a call to this function). After this function returns,
no function other than <tt>sane_init()</tt> may be called (regardless
of the status value returned by <tt>sane_exit()</tt>. Neglecting to
call this function may result in some resources not being released
properly.
<blockquote><a name="i83">
<pre>
void sane_exit (void);
</pre>
</blockquote>
<p><h3><a name="s4.3.3">4.3.3 <tt>sane_get_devices</tt></a></h3>
<p>This function can be used to query the list of devices that are
available. If the function executes successfully, it stores a pointer
to a <tt>NULL</tt> terminated array of pointers to <tt>SANE_Device</tt>
structures in <tt>*device_list</tt>. The returned list is guaranteed
to remain unchanged and valid until (a) another call to this function
is performed or (b) a call to <tt>sane_exit()</tt> is performed. This
function can be called repeatedly to detect when new devices become
available. If argument <tt>local_only</tt> is true, only local devices
are returned (devices directly attached to the machine that SANE is
running on). If it is false, the device list includes all remote
devices that are accessible to the SANE library.
<blockquote><a name="i84">
<pre>
SANE_Status sane_get_devices (const SANE_Device *** device_list,
SANE_Bool local_only);
</pre>
</blockquote>
<p>This function may fail with <tt>SANE_STATUS_NO_MEM</tt> if an
insufficient amount of memory is available.
<p><blockquote>
<center>
<b>Backend Implementation Note</b>
</center>
SANE does not require that this function is called before a
<tt>sane_open()</tt> call is performed. A device name may be
specified explicitly by a user which would make it unnecessary and
undesirable to call this function first.
<font color="darkgreen">
The same information about
a device has to be returned when <tt>sane_open</tt> is called.
</font>
</blockquote>
<p><h3><a name="s4.3.4">4.3.4 <tt>sane_open</tt></a></h3>
<p>This function is used to establish a connection to a particular
device. The name of the device to be opened is passed in argument
<tt>name</tt>. If the call completes successfully, a handle for the
device is returned in <tt>*h</tt>.
<font color="darkgreen">
The description of the device
is returned in <tt>**device_description</tt>. This is the
same description that is returned in the list by <tt>sane_get_devices</tt>.
The returned data <tt>*h</tt> and <tt>*device_description</tt> is guaranteed
to remain unchanged and valid until a call to <tt>sane_close()</tt>
is performed.
</font>
As a special case, specifying a zero-length string as the device requests
opening the first available device (if there is such a device).
<blockquote><a name="i85">
<pre>
SANE_Status sane_open (SANE_String_Const name, SANE_Handle * h,
const SANE_Device ** device_description);
</pre>
</blockquote>
<p>This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_DEVICE_BUSY</tt>:<dd> The device is currently
busy (in use by somebody else).
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> The device name is not valid.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occured while
communicating with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_ACCESS_DENIED</tt>:<dd> Access to the device has
been denied due to insufficient or invalid authentication.
</dl>
</blockquote>
<p><h3><a name="s4.3.5">4.3.5 <tt>sane_close</tt></a></h3>
<p>This function terminates the association between the device handle
passed in argument <tt>h</tt> and the device it represents. If the
device is presently active, a call to <tt>sane_cancel()</tt> is
performed first. After this function returns, handle <tt>h</tt> must
not be used anymore.
<p><blockquote><a name="i86">
<pre>
void sane_close (SANE_Handle h);
</pre>
</blockquote>
<p><h3><a name="s4.3.6">4.3.6 <tt>sane_get_option_descriptor</tt></a></h3>
<p>This function is used to access option descriptors. The function
returns the option descriptor for option number <tt>n</tt> of the device
represented by handle <tt>h</tt>. Option number 0 is guaranteed to be a
valid option. Its value is an integer that specifies the number of
options that are available for device handle <tt>h</tt> (the count
includes option 0). If n is not a valid option index, the function
returns <tt>NULL</tt>. The returned option descriptor is guaranteed to
remain valid (and at the returned address) until the device is closed.
<p><blockquote><a name="i87">
<pre>
const SANE_Option_Descriptor *
sane_get_option_descriptor (SANE_Handle h, SANE_Int n);
</pre>
</blockquote>
<p><h3><a name="s4.3.7">4.3.7 <tt>sane_control_option</tt></a></h3>
<p>This function is used to set or inquire the current value of option
number <tt>n</tt> of the device represented by handle <tt>h</tt>. The
manner in which the option is controlled is specified by parameter
<tt>a</tt>. The possible values of this parameter are described in more
detail below. The value of the option is passed through argument
<tt>v</tt>. It is a pointer to the memory that holds the option value.
The memory area pointed to by <tt>v</tt> must be big enough to hold the
entire option value (determined by member <tt>size</tt> in the
corresponding option descriptor). The only exception to this rule is
that when setting the value of a string option, the string pointed to
by argument <tt>v</tt> may be shorter since the backend will stop
reading the option value upon encountering the first <tt>NUL</tt>
terminator in the string. If argument <tt>i</tt> is not <tt>NULL</tt>,
the value of <tt>*i</tt> will be set to provide details on how well the
request has been met. The meaning of this argument is described in
more detail below.
<blockquote><a name="i88">
<pre>
SANE_Status sane_control_option (SANE_Handle h, SANE_Int n,
SANE_Action a, void *v,
SANE_Int * i);
</pre>
</blockquote>
<p>The way the option is affected by a call to this function is
controlled by parameter <tt>a</tt> which is a value of type
<tt>SANE_Action<a name="i89"></tt>. The possible values and their meaning is
described in Table <a href="doc012.html#t7">7</a>.
<p><p><a name="t7"></a>
<center>
<table cellpadding=0 cellspacing=0 border=1>
<tr valign=top>
<td colspan=1 align=center nowrap><b>Symbol</b></td>
<td colspan=1 align=center nowrap><b>Code</b></td>
<td colspan=1 align=center nowrap><b>Description</b></td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
<p><tt>SANE_ACTION_GET_VALUE<a name="i90"></tt> </td>
<td colspan=1 align=right nowrap> 0 </td>
<td colspan=1 align=left> Get current option value. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_ACTION_SET_VALUE<a name="i91"></tt> </td>
<td colspan=1 align=right nowrap> 1 </td>
<td colspan=1 align=left> Set option value. The
option value passed through argument <tt>v</tt> may be modified by the
backend if the value cannot be set exactly. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_ACTION_SET_AUTO<a name="i92"></tt> </td>
<td colspan=1 align=right nowrap> 2 </td>
<td colspan=1 align=left> Turn on automatic mode. Backend
or device will automatically select an appropriate value. This mode
remains effective until overridden by an explicit set value request.
The value of parameter <tt>v</tt> is completely ignored in this case and
may be <tt>NULL</tt>. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
</td></tr>
</table>
<p><center>Table 7: Action Values (<tt>SANE_Action</tt>)</center>
</center>
<p>
<p>After setting a value via an action value of
<tt>SANE_ACTION_SET_VALUE</tt>, additional information on how well the
request has been met is returned in <tt>*i</tt> (if <tt>i</tt> is
non-<tt>NULL</tt>). The returned value is a bitset that may contain any
combination of the values described in Table <a href="doc012.html#t8">8</a>.
<p><a name="t8"></a>
<center>
<table cellpadding=0 cellspacing=0 border=1>
<tr valign=top>
<td colspan=1 align=center nowrap><b>Symbol</b></td>
<td colspan=1 align=center nowrap><b>Code</b></td>
<td colspan=1 align=center nowrap><b>Description</b></td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
<p><tt>SANE_INFO_INEXACT<a name="i93"></tt> </td>
<td colspan=1 align=right nowrap> 1 </td>
<td colspan=1 align=left> This value is returned when
setting an option value resulted in a value being selected that does
not exactly match the requested value. For example, if a scanner
can adjust the resolution in increments of 30dpi only, setting the
resolution to 307dpi may result in an actual setting of 300dpi.
When this happens, the bitset returned in <tt>*i</tt> has this member
set. In addition, the option value is modified to reflect the
actual (rounded) value that was used by the backend. Note that
inexact values are admissible for strings as well. A backend may
choose to ``round'' a string to the closest matching legal string
for a constrained string value. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_INFO_RELOAD_OPTIONS<a name="i94"></tt> </td>
<td colspan=1 align=right nowrap> 2 </td>
<td colspan=1 align=left> The setting of an
option may affect the value or availability of one or more <em>
other</em> options. When this happens, the SANE backend sets this
member in <tt>*i</tt> to indicate that the application should reload
all options. This member may be set if and only if at least one
option changed. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_INFO_RELOAD_PARAMS<a name="i95"></tt> </td>
<td colspan=1 align=right nowrap> 4 </td>
<td colspan=1 align=left> The setting of an option may
affect the parameter values (see <tt>sane_get_parameters()</tt>).
If setting an option affects the parameter values, this member will
be set in <tt>*i</tt>. Note that this member may be set even if the
parameters did not actually change. However, it is guaranteed that
the parameters never change without this member being set. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
</td></tr>
</table>
<p><center>Table 8: Additional Information Returned When Setting an Option</center>
</center>
<p>
<p>This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_UNSUPPORTED</tt>:<dd> The operation is not
supported for the specified handle and option number.
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> The option value is not valid.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occured while
communicating with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_ACCESS_DENIED</tt>:<dd> Access to the option has
been denied due to insufficient or invalid authentication.
</dl>
</blockquote>
<p><h3><a name="s4.3.8">4.3.8 <tt>sane_get_parameters</tt></a></h3>
<p>This function is used to obtain the current scan parameters. The
returned parameters are guaranteed to be accurate between the time a
scan has been started (<tt>sane_start()</tt> has been called) and the
completion of that request. Outside of that window, the returned
values are best-effort estimates of what the parameters will be when
<tt>sane_start()</tt> gets invoked. Calling this function before a
scan has actually started allows, for example, to get an estimate of
how big the scanned image will be. The parameters passed to this
function are the handle <tt>h</tt> of the device for which the
parameters should be obtained and a pointer <tt>p</tt> to a parameter
structure. The parameter structure is described in more detail below.
<p><blockquote><a name="i96">
<pre>
SANE_Status sane_get_parameters (SANE_Handle h,
SANE_Parameters * p);
</pre>
</blockquote>
<p>The scan parameters are returned in a structure of type
<tt>SANE_Parameters<a name="i97"></tt>. The C declaration of this structure
is given below.
<font color="darkgreen">
<blockquote>
<pre>
typedef struct
{
SANE_Frame format;
SANE_Int flags;
SANE_Int lines;
SANE_Int depth;
SANE_Int pixels_per_line;
SANE_Int bytes_per_line;
SANE_Int channels_per_image;
SANE_String format_desc;
SANE_String proposed_filename;
SANE_Int dpi_x;
SANE_Int dpi_y;
char reserved[32]; /* 32 bytes for future use */
}
SANE_Parameters;
</pre>
</blockquote>
</font>
<p><font color="darkgreen">
Member <tt>format</tt> specifies the format of the next frame to be
returned. The possible values for type <tt>SANE_Frame<a name="i98"></tt> are
described in Table <a href="doc012.html#t9">9</a>. The meaning of these
values is described in more detail in Section <a href="doc008.html#s3.2">3.2</a>.
<p><a name="t9"></a>
<center>
<table cellpadding=0 cellspacing=0 border=1>
<tr valign=top>
<td colspan=1 align=center nowrap><b>Symbol</b></td>
<td colspan=1 align=center nowrap><b>Code</b></td>
<td colspan=1 align=center nowrap><b>SANE standard</b></td>
<td colspan=1 align=center nowrap><b>Description</b></td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
<p><tt>SANE_FRAME_GRAY<a name="i99"></tt> </td>
<td colspan=1 align=center nowrap> 0 </td>
<td colspan=1 align=center nowrap> version 1 </td>
<td colspan=1 align=left nowrap> Band covering human visual range. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_FRAME_RGB<a name="i100"></tt> </td>
<td colspan=1 align=center nowrap> 1 </td>
<td colspan=1 align=center nowrap> version 1 </td>
<td colspan=1 align=left nowrap> Pixel-interleaved red/green/blue bands. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_FRAME_RED<a name="i101"></tt> </td>
<td colspan=1 align=center nowrap> 2 </td>
<td colspan=1 align=center nowrap> version 1 </td>
<td colspan=1 align=left nowrap> Red band of a red/green/blue image. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_FRAME_GREEN<a name="i102"></tt> </td>
<td colspan=1 align=center nowrap> 3 </td>
<td colspan=1 align=center nowrap> version 1 </td>
<td colspan=1 align=left nowrap> Green band of a red/green/blue image. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_FRAME_BLUE<a name="i103"></tt> </td>
<td colspan=1 align=center nowrap> 4 </td>
<td colspan=1 align=center nowrap> version 1 </td>
<td colspan=1 align=left nowrap> Blue band of a red/green/blue image. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_FRAME_RAW<a name="i104"></tt> </td>
<td colspan=1 align=center nowrap> 5 </td>
<td colspan=1 align=center nowrap> version 2 </td>
<td colspan=1 align=left nowrap> Arbitrary pixel property transmission. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_FRAME_MIME<a name="i105"></tt> </td>
<td colspan=1 align=center nowrap> 6 </td>
<td colspan=1 align=center nowrap> version 2 </td>
<td colspan=1 align=left nowrap> Data described by a mime descriptor. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
</td></tr>
</table>
<p><center>Table 9: Frame Format (<tt>SANE_Frame</tt>)</center>
</center>
<p>
<p>The <tt>flags</tt> member is a 32 bit bitfield, for which up to now 4
informational bits are defined, all unused bits have to be set to 0:
<p><ul>
<p><li>
<tt>SANE_PFLAG_LAST_FRAME</tt> (bit 0, bitvalue 1) is set to 1 if and
only if the frame that is currently being acquired (or the frame that
will be acquired next if there is no current frame) is the last frame
of a multi frame image (e.g., the current frame is the blue component
of a red, green, blue image). Note, that it is possible to transmit
multiple images in succession.
<p><li>
<tt>SANE_PFLAG_MORE_IMAGES</tt> (bit 1, bitvalue 2) is set to 1 to indicate
further pending images. It is permissible to set that value to 1 "in good
faith", as it has to be determined at a very early time, where it might
not be detectable, if there actually are more images to transfer. E.g.
you will usually not know if the document feeder contains further pages
when starting to scan the current one. Thus you are allowed to set that
bit but later fail at <tt>sane_start()</tt>.
<p><li>
<tt>SANE_PFLAG_NEW_PAGE</tt> (bit 2, bitvalue 4) is set to 1 to indicate
that the current frame comes from a new physical page. This bit is of
informational character only to help frontends to group multi-image
scans.
<p><li>
<tt>SANE_PFLAG_BACKSIDE</tt> (bit 3, bitvalue 8) tells if the current image
was acquired from the front (0) or backside (1) of the currently processed
sheet. It is of informational character and allows to group and order
multi-image transfers regardless of scanner acquisition order (front
first/back first).
<p></ul>
<p>Note, that <tt>flags</tt> is compatible to member <tt>last_frame</tt> of
<tt>SANE_Parameters</tt> of SANE standard version 1 (same size
and only bit 0 (bitvalue 1) was used with same function).
<p>Member <tt>lines</tt> specifies how many scan lines the frame is
comprised of. If this value is -1, the number of lines is not known a
priori and the frontend should call <tt>sane_read()</tt> until it
returns a status of <tt>SANE_STATUS_EOF</tt>.
Note, that even when transferring formats that have this information
inband, it is recommended to set that member, if available. If
unavailable or not applicable, set to -1 as mentioned above.
<p>Member <tt>bytes_per_line</tt> specifies the number of bytes that
comprise one scan line.
If <tt>bytes_per_line</tt> is set to 0, which can currently only be the case for
<tt>SANE_FRAME_MIME</tt>, the frontend shall not assume a constant line
length. Instead it should simply try to read until <tt>SANE_STATUS_EOF</tt>
with an arbitrary block length.
<p>Member <tt>depth</tt> specifies the number of bits per sample.
Note, that only 0 (for not applicable), 1, and n*8 are allowed
values. Data with other depths has to be scaled up accordingly.
<p>Member <tt>pixels_per_line</tt> specifies the number of pixels that
comprise one scan line.
<p>Assume B is the number of channels in the frame, then the bit depth
d (as given by member <tt>depth</tt>) and the number of pixels per
line n (as given by this member <tt>pixels_per_line</tt>) are
related to c, the number of bytes per line (as given by member
<tt>bytes_per_line</tt>) as follows:
<p>
<center>
c &gt;= \left{
ll
\lceil B*n / 8\rceil if d=1
</td><td align=right>(1)</td></tr><tr><td align=center>
B*n *\lceil (d + 7)/8 \rceil if d&gt;1
\right.
</center>
<p>
Note that the number of bytes per line can be larger than the minimum
value imposed by the right side of this equation. A frontend must be
able to properly cope with such ``padded'' image formats.
<p>Member <tt>channels_per_image</tt> specifies the number of channels the
image consists of. When the image is transmitted in more than one frame
<tt>channels_per_image</tt> has to be the same for all frames for this image.
<p>Member <tt>format_desc</tt> is used for the new frametypes
<tt>SANE_FRAME_RAW</tt> and <tt>SANE_FRAME_MIME</tt>. Its meaning differs
between the two types:
<p><ul>
<li>
<tt>SANE_FRAME_RAW</tt>:
The <tt>format_desc</tt> contains a description of the channel data and
an optional depth information separated by a colon(:).
<p>A plane is descibed by one channel, e.g. "<tt>gray</tt>" or "<tt>gray:12</tt>".
<p>Channel interleaved data is described by a comma separated list of channel descriptions,
for example "<tt>red,green,blue</tt>" or "<tt>red:8,green:8,blue:8</tt>",
the channel data is sent in the given order.
<p>The depth information does <b>not</b> define the size of the transmitted
channel data, it is only an information for the frontend. The channel data has
to be sent in the size defined by member <tt>depth</tt>.
<p>Well known channels are <tt>red</tt>, <tt>green</tt>, <tt>blue</tt> and <tt>gray</tt>.
It also is allowed to use other channel descriptions, e.g. if you
use an infrared camera or scanner it could be <tt>infrared</tt> or
a wavelength description like <tt>1100nm</tt>, but be aware that a
frontend may not be able to display such channels with useful colors.
<p>Note that an image can be sent in single planes, in one interleaved
frame that contains all channels or in several frames that contain
one or more (interleaved) channels. When an RGB image is sent it
is prefered to send the image data in one interleaved frame
that consist of red, green and blue data in this order.
The number of channels is defined in member <tt>channels_per_image</tt>.
<p><li>
<tt>SANE_FRAME_MIME</tt>:
The <tt>format_desc</tt> contains the MIME type/subtype *(;parameter)
fields as described in RFC 1521, 4. The Content-Type header field,
without the prefixing "Content-Type:".
Note, that it is discouraged to transfer proprietary file formats over
SANE. If at all possible, please stick to the IANA assigned MIME types,
and make sure the data stream is compliant with the corresponding
specification.
When data is transmitted with the frame type <tt>SANE_FRAME_MIME</tt>
all data has to be transmitted within one frame, multiple frames
are not allowed (so the flag <tt>last_frame</tt> has to be set
when using this frame type).
A fully compliant SANE backend is required to transmit in either
SANE native frametypes, or in a MIME type, for which a converting
meta backend exists and is freely available for all platforms.
<p>Other formats may be transmitted, but the only thing the average
frontend can do with them, is save them. This is not considered a
good option, as it does not facilitate transmitting the data to a
client application that may be running the frontend.
However, if the data transferred by the backend is not an image in
nature, it wouldn't make sense to try converting it anyway, so it is
acceptable to use a simple <tt>SANE_FRAME_MIME</tt> transfer for that
case. But even then, try to stick to well known stuff with freely
existing standards and viewers as well.
</ul>
<p>The member <tt>proposed_filename</tt> can be used to suggest a reasonable
default filename or -extension in case the backend can make such a
suggestion, like e.g. an image database.
If no such suggestion is intended, set the field to "".
<p>In the case of raw frames, <tt>proposed_filename</tt> is expected to hold
the basename for the image, with the extension determined by the save function
of the frontend, as the frontend can fully understand the data and is thus
able to encode it in any format it wishes.
<p>For MIME frames <tt>proposed_filename</tt> can contain either:
<p><ul>
<li>
A name with a leading dot, which is considered to be a proposed
filename extension. This could also be gotten from the mime database,
but for systems lacking it, this might be convenient. Or:
<p><li>
A complete filename, including extension.
</ul>
<p>Note, that for frontends that are able to parse a given MIME type
internally, it is perfectly permissible to ignore the extension
part of the proposed filename and only make use of the basename,
when using internal save algorithms for different formats.
<p>In any case, if the frontend makes use of this field, the frontend
must mangle this proposal or the final filename it produces with
its help to suit local filesystem restrictions.
<p>Special care should be taken not to cause security flaws this way.
For Unix, that means killing out all path separators (/) [to avoid
to save away stuff in obscure places or create critical files like
/etc/hosts.allow] and avoiding to overwrite existing files.
(Creating of leading dot files - like .rhosts - is not an issue here,
because that's only a proposed filename extension as mentioned above.
<p>The string <tt>proposed_comment</tt> can be used to transmit additional
image data, that can be stored in the comment areas several fileformats
offer. It can contain any textual information the backend wishes to
convey to the user, like date/time of exposure, enganged filters,
etc.
<p>The members <tt>dpi_x, dpi_y</tt> encode the horizontal and vertical
resolution. Note, that multiple-image scans may have different
resolutions of each image. It is not permissible to change resolution
between frames of the same image.
<p>The member <tt>reserved</tt> is an array of 32 bytes (char) to keep
the size of the struct unchanged when future extensions are done.
The backend has to set the reserved bytes to 0.
</font>
<p><h3><a name="s4.3.9">4.3.9 <tt>sane_start</tt></a></h3>
<p>This function initiates aquisition of an image from the device
represented by handle <tt>h</tt>.
<blockquote><a name="i106">
<pre>
SANE_Status sane_start (SANE_Handle h);
</pre>
</blockquote>
This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_CANCELLED</tt>:<dd> The operation was cancelled through
a call to <tt>sane_cancel</tt>.
<dt><tt>SANE_STATUS_DEVICE_BUSY</tt>:<dd> The device is busy. The
operation should be retried later.
<dt><tt>SANE_STATUS_JAMMED</tt>:<dd> The document feeder is jammed.
<dt><tt>SANE_STATUS_NO_DOCS</tt>:<dd> The document feeder is out of
documents.
<dt><tt>SANE_STATUS_COVER_OPEN</tt>:<dd> The scanner cover is open.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occurred while communicating
with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> The scan cannot be started with the current
set of options. The frontend should reload the option descriptors, as if
<tt>SANE_INFO_RELOAD_OPTIONS<a name="i107"></tt> had been returned from a call to
<tt>sane_control_option()</tt>, since the device's capabilities may have
changed.
</dl>
</blockquote>
<p><h3><a name="s4.3.10">4.3.10 <tt>sane_read</tt></a></h3>
<p>This function is used to read image data from the device represented
by handle <tt>h</tt>. Argument <tt>buf</tt> is a pointer to a memory area
that is at least <tt>maxlen</tt> bytes long. The number of bytes
returned is stored in <tt>*len</tt>. A backend must set this to zero
when a status other than <tt>SANE_STATUS_GOOD</tt> is returned).
When the call succeeds, the number of bytes returned can be anywhere in
the range from 0 to <tt>maxlen</tt> bytes.
<blockquote><a name="i108">
<pre>
SANE_Status sane_read (SANE_Handle h, SANE_Byte * buf,
SANE_Int maxlen, SANE_Int * len);
</pre>
</blockquote>
For efficiency reasons, medium to large
block sizes (in the range of a few kilobytes) should be used.
Returning short reads is allowed to allow for small buffers
in the backend.
If this function is called when no data is available, one of two
things may happen, depending on the I/O mode that is in effect for
handle <tt>h</tt>.
<ol>
<li>If the device is in blocking I/O mode (the default mode), the
call blocks until at least one data byte is available (or until some
error occurs).
<p><li>If the device is in non-blocking I/O mode, the call returns
immediately with status <tt>SANE_STATUS_GOOD</tt> and with
<tt>*len</tt> set to zero.
</ol>
The I/O mode of handle <tt>h</tt> can be set via a call to
<tt>sane_set_io_mode()</tt>.
<p>This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_CANCELLED</tt>:<dd> The operation was cancelled through
a call to <tt>sane_cancel</tt>.
<dt><tt>SANE_STATUS_EOF</tt>:<dd> No more data is available for the
current frame. If <tt>sane_read</tt> sends back any image data it
is not allowed to return with <tt>SANE_STATUS_EOF</tt>.
<dt><tt>SANE_STATUS_JAMMED</tt>:<dd> The document feeder is jammed.
<dt><tt>SANE_STATUS_NO_DOCS</tt>:<dd> The document feeder is out of
documents.
<dt><tt>SANE_STATUS_COVER_OPEN</tt>:<dd> The scanner cover is open.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occurred while communicating
with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_ACCESS_DENIED</tt>:<dd> Access to the device has
been denied due to insufficient or invalid authentication.
</dl>
</blockquote>
<p><h3><a name="s4.3.11">4.3.11 <tt>sane_cancel</tt></a></h3>
<p>This function is used to immediately or as quickly as possible cancel
the currently pending operation of the device represented by handle
<tt>h</tt>.
<blockquote><a name="i109">
<pre>
void sane_cancel (SANE_Handle h);
</pre>
</blockquote>
This function can be called at any time (as long as handle <tt>h</tt> is
a valid handle) but usually affects long-running operations only (such
as image is acquisition). It is safe to call this function
asynchronously (e.g., from within a signal handler). It is important
to note that completion of this operaton does <em>not</em> imply that
the currently pending operation has been cancelled. It only
guarantees that cancellation has been <em>initiated</em>. Cancellation
completes only when the cancelled call returns (typically with a
status value of <tt>SANE_STATUS_CANCELLED</tt>). Since the SANE API
does not require any other operations to be re-entrant, this implies
that a frontend must <em>not</em> call any other operation until the
cancelled operation has returned.
<p><h3><a name="s4.3.12">4.3.12 <tt>sane_set_io_mode</tt></a></h3>
<p>This function is used to set the I/O mode of handle <tt>h</tt>. The I/O mode
can be either blocking or non-blocking. If argument <tt>m</tt> is
<tt>SANE_TRUE</tt>, the mode is set to non-blocking mode, otherwise it's set to
blocking mode. This function can be called only after a call to
<tt>sane_start()</tt> has been performed.
<blockquote><a name="i110">
<pre>
SANE_Status sane_set_io_mode (SANE_Handle h, SANE_Bool m);
</pre>
</blockquote>
By default, newly opened handles operate in blocking mode. A backend
may elect not to support non-blocking I/O mode. In such a case the
status value <tt>SANE_STATUS_UNSUPPORTED</tt> is returned. Blocking
I/O must be supported by all backends, so calling this function with
argument <tt>m</tt> set to <tt>SANE_FALSE</tt> is guaranteed to complete
successfully.
<p>This function may fail with one of the following status codes:
<blockquote>
<dl>
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> No image acquisition is pending.
<dt><tt>SANE_STATUS_UNSUPPORTED</tt>:<dd> The backend does not support
the requested I/O mode.
</dl>
</blockquote>
<p><h3><a name="s4.3.13">4.3.13 <tt>sane_get_select_fd</tt></a></h3>
<p>This function is used to obtain a (platform-specific) file-descriptor
for handle <tt>h</tt> that is readable if and only if image data is
available (i.e., when a call to <tt>sane_read()</tt> will return at
least one byte of data). If the call completes successfully, the
select file-descriptor is returned in <tt>*fd</tt>.
<blockquote><a name="i111">
<pre>
SANE_Status sane_get_select_fd (SANE_Handle h, SANE_Int *fd);
</pre>
</blockquote>
This function can be called only after a call to <tt>sane_start()</tt>
has been performed and the returned file-descriptor is guaranteed to
remain valid for the duration of the current image acquisition (i.e.,
until <tt>sane_cancel()</tt> or <tt>sane_start()</tt> get called again
or until <tt>sane_read()</tt> returns with status
<tt>SANE_STATUS_EOF</tt>). Indeed, a backend must guarantee to
close the returned select file descriptor at the point when the next
<tt>sane_read()</tt> call would return <tt>SANE_STATUS_EOF</tt>.
This is necessary to ensure the application can detect when this
condition occurs without actually having to call <tt>sane_read()</tt>.
<p>A backend may elect not to support this operation. In such a case,
the function returns with status code
<tt>SANE_STATUS_UNSUPPORTED</tt>.
<p>Note that the only operation supported by the returned file-descriptor
is a host operating-system dependent test whether the file-descriptor
is readable (e.g., this test can be implemented using <tt>select()</tt>
or <tt>poll()</tt> under UNIX). If any other operation is performed on
the file descriptor, the behavior of the backend becomes
unpredictable. Once the file-descriptor signals ``readable'' status,
it will remain in that state until a call to <tt>sane_read()</tt> is
performed. Since many input devices are very slow, support for this
operation is strongly encouraged as it permits an application to do
other work while image acquisition is in progress.
<p>This function may fail with one of the following status codes:
<blockquote>
<dl>
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> No image acquisition is pending.
<dt><tt>SANE_STATUS_UNSUPPORTED</tt>:<dd> The backend does not support
this operation.
</dl>
</blockquote>
<p><h3><a name="s4.3.14">4.3.14 <tt>sane_strstatus</tt></a></h3>
<p>This function can be used to translate a SANE status code into a
printable string. The returned string is a single line of text that
forms a complete sentence, but without the trailing period
(full-stop). The function is guaranteed to never return <tt>NULL</tt>.
The returned pointer is valid at least until the next call to this
function is performed.
<blockquote><a name="i112">
<pre>
const SANE_String_Const sane_strstatus (SANE_Status status);
</pre>
</blockquote>
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<hr>
<title>Code Flow</title>
<h2><a name="s4.4">4.4 Code Flow</a></h2><a name="i113">
<p>The code flow for the SANE API is illustrated in
Figure <a href="doc013.html#f4">4</a>. Functions <tt>sane_init()</tt> and
<tt>sane_exit()</tt> initialize and exit the backend, respectively.
All other calls must be performed after initialization and before
exiting the backend.
<p><p><a name="f4"></a>
<center>
<img width=566 height=510 src="img003.gif">
<p><center>Figure 4: Code flow</center>
</center>
<p>
<p>Function <tt>sane_get_devices()</tt> can be called any time after
<tt>sane_init()</tt> has been called. It returns the list of the
devices that are known at the time of the call. This list may change
over time since some devices may be turned on or off or a remote host
may boot or shutdown between different calls. It should be noted that
this operation may be relatively slow since it requires contacting all
configured devices (some of which may be on remote hosts). A frontend
may therefore want to provide the ability for a user to directly
select a desired device without requiring a call to this function.
<p>Once a device has been chosen, it is opened using a call to
<tt>sane_open()</tt>. Multiple devices can be open at any given time.
A SANE backend must not impose artificial constraints on how many
devices can be open at any given time.
<p>An opened device can be setup through the corresponding device handle
using functions <tt>sane_get_option_descriptor()</tt> and
<tt>sane_control_option()</tt>. While setting up a device, obtaining
option descriptors and setting and reading of option values can be
mixed freely. It is typical for a frontend to read out all available
options at the beginning and then build a dialog (either graphical or
a command-line oriented option list) that allows to control the
available options. It should be noted that the number of options is
fixed for a given handle. However, as options are set, other options
may become active or inactive. Thus, after setting an option, it
may be necessary to re-read some or all option descriptors. While
setting up the device, it is also admissible to call
<tt>sane_get_parameters()</tt> to get an estimate of what the image
parameters will look like once image acquisition begins.
<p>The device handle can be put in blocking or non-blocking mode by a
call to <tt>sane_set_io_mode()</tt>. Devices are required to support
blocking mode (which is the default mode), but support for
non-blocking I/O is strongly encouraged for operating systems such as
UNIX.
<p>After the device is setup properly, image acquisition can be started
by a call to <tt>sane_start()</tt>. The backend calculates the exact
image parameters at this point. So future calls to
<tt>sane_get_parameters()</tt> will return the exact values, rather
than estimates. Whether the physical image acquisition starts at this
point or during the first call to <tt>sane_read()</tt> is unspecified
by the SANE API. If non-blocking I/O and/or a select-style interface
is desired, the frontend may attempt to call
<tt>sane_set_io_mode()</tt> and/or <tt>sane_get_select_fd()</tt> at
this point. Either of these functions may fail if the backend does
not support the requested operation.
<p><font color="darkgreen">
Image data is collected by repeatedly calling <tt>sane_read()</tt>
until this function will return an end-of-file status
(<tt>SANE_STATUS_EOF</tt>). This indicates the end of the current
frame. If the frontend expects additional frames (e.g., the
individual channels of a red/green/blue image or multiple images),
it can call <tt>sane_start()</tt> again.
If the <tt>SANE_PFLAG_LAST_FRAME</tt> bit is set in <tt>flags</tt>, the
current image is complete. In this case, it should be tested, if
<tt>flags</tt> has the <tt>SANE_PFLAG_MORE_IMAGES</tt> bit set.
If yes, further calls to <tt>sane_start()</tt> can be made to acquire
more images. Please note, that as this bit has to be set at the beginning
of a the transmission of the last frame before the new image, it is possible,
that no reliable decision can be made at this time. It is thus permissible
for a backend to set this bit, and then later at the actual call to
<tt>sane_start()</tt> return an error like <tt>SANE_STATUS_NO_DOCS</tt>.
Such a sequence is permitted to transmit multiple images from a single
page as well as multiple pages. This behaviour should be controlled by
backend options as required, to allow single-page scanning as well as
ADF-batch-scanning. The frontend should always continue reading all images
until a frame with <tt>SANE_PFLAG_LAST_FRAME</tt> on
and <tt>SANE_PFLAG_MORE_IMAGES</tt> off is encountered, or an error other
than <tt>SANE_STATUS_EOF</tt> occurs in a SANE function.
Note that <tt>SANE_STATUS_NO_DOCS</tt> also is an allowed way for the backend
to indicate the end of a multiple image scan.
<p>A frontend may choose to skip frames (e.g. because it cannot parse them),
which is accomplished by simply calling <tt>sane_start</tt> again, which will get
you to the next frame, without having to read and discard the current one.
<p>In order to prematurely stop scanning and to reset the backend state,
<tt>sane_cancel()</tt> can be called at any time. This call is required
as well after normal termination of a multiple image scan as described above.
<p>When done using the device, the handle should be closed by a call to
<tt>sane_close()</tt>. Finally, before exiting the application,
function <tt>sane_exit()</tt> must be called. It is important not to
forget to call this function since otherwise some resources (e.g.,
temporary files or locks) may remain unclaimed.
<p>The following C sample code implements a reference loop for acquiring
multiple images:
<p><pre>
SANE_Parameters parms;
SANE_Status status;
do
{
do
{
/* Now start acquiring the next frame. */
status=sane_start(handle);
/* if that failed, we have a problem, and no more frames can be
* read at this time. Due to SANE_PFLAG_MORE_IMAGES still
* being clear, this will break out of _BOTH_ loops.
*/
if (status != SANE_STATUS_GOOD) break;
/* Now let us see what the next frame brings. */
status=sane_get_parameters(handle,&amp;parms);
/* This actually should not fail, but maybe the doc feeder
* jammed or something, so we break as well, if something
* is wrong.
*/
if (status != SANE_STATUS_GOOD) break;
/* Now we check the announced parameters, if we can make use
* of the frame data. If not, we skip over to the next frame.
*/
if ( do_i_like_that(&amp;parms) == NO ) continue;
/* Set up for reading the data here. Mangle filenames,
* allocate memory, rewind multiframe files, ask user
* for confirmation, ...
*/
setup_for_transfer(...);
/* Now we read in the frame data and process it. This should
* return SANE_STATUS_GOOD, until the frame is complete,
* what causes SANE_STATUS_EOF to be returned.
*/
while( SANE_STATUS_GOOD == ( status=sane_read(...) ) )
read_in_and_process_data_as_required();
/* If transfer was broken due to anything but EOF, break out. */
if (status != SANE_STATUS_EOF) {
break;
}
/* Now loop until we have all frames of an image. */
} while(!(parms.flag &amp; SANE_PFLAG_LAST_FRAME));
/* O.K. - we now have a complete image. Fit it together, save it,
* flush buffers, transmit it, increment filenames, etc.
*/
/* Now check for more pending images. If we have more, redo from start.
* Some backends might cheat here and send us for an extra round which
* will fail at sane_start, as they were not able to determine if they
* would have more data at the start of the last frame we read.
*/
} while(parms.flags &amp; SANE_PFLAG_MORE_IMAGES);
/* No more data. Fine. Reset the backend and go back to option-control
* loop.
*/
sane_cancel(handle);
</pre>
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<title>Well-Known Options</title>
<h2><a name="s4.5">4.5 Well-Known Options</a></h2><a name="i114">
<p>While most backend options are completely self-describing, there are
cases where a user interface might want to special-case the handling
of certain options. For example, the scan area is typically defined
by four options that specify the top-left and bottom-right corners of
the area. With a graphical user interface, it would be tedious to
force the user to type in these four numbers. Instead, most such
interfaces will want to present to the user a preview (low-resolution
scan of the full scanner surface or a high(er) resolution scan of a subpart
of the scanner surface) and let the user pick the scan area by
dragging a rectangle into the desired position. For this reason, the
SANE API specifies a small number of option names that have
well-defined meanings.
<p><h3><a name="s4.5.1">4.5.1 Option Number Count</a></h3><a name="i115">
<p>Option number 0 has an empty string as its name. The value of this
option is of type <tt>SANE_TYPE_INT</tt> and it specifies the total
number of options available for a given device (the count includes
option number 0). This means that there are two ways of counting the
number of options available: a frontend can either cycle through all
option numbers starting at one until
<tt>sane_get_option_descriptor()</tt> returns <tt>NULL</tt>, or a
frontend can directly read out the value of option number 0.
<p><h3><a name="s4.5.2">4.5.2 Scan Resolution Options</a></h3><a name="i116"><a name="i117">
<p><font color="darkgreen">
Option <tt>resolution</tt> is used to select the resolution at which an
image should be acquired. When the backend wants to allow different
values for x- and y-resolution it has to define the options
<tt>x_resolution</tt> and <tt>y_resolution</tt>. Note that only
the option <tt>resolution</tt> <b>or</b> the options
<tt>x_resolution</tt> <b>and</b> <tt>y_resolution</tt> may be active.
<p>The type of this option is either <tt>SANE_TYPE_INT</tt> or
<tt>SANE_TYPE_FIXED</tt>. The unit is <tt>SANE_UNIT_DPI</tt> (dots/inch).
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<p><h3><a name="s4.5.3">4.5.3 Preview Mode Option</a></h3><a name="i118">
<p>The boolean option <tt>preview</tt> is used by a frontend to inform the
backend when image acquisition should be optimized for speed, rather
than quality (``preview mode''). When set to <tt>SANE_TRUE</tt>,
preview mode is in effect, when set to <tt>SANE_FALSE</tt> image
acquisition should proceed in normal quality mode. The setting of
this option <em>must not</em> affect any other option. That is, as
far as the other options are concerned, the preview mode is completely
side effect free. A backend can assume that the frontend will take
care of appropriately setting the scan resolution for preview mode
(through option <tt>resolution</tt>). A backend is free to override the
<tt>resolution</tt> value with its own choice for preview mode, but it
is advised to leave this choice to the frontend wherever possible.
<font color="darkgreen">
When the <tt>preview</tt> option is set the backend should transfer
the image in frame type <tt>SANE_FRAME_RAW</tt> if possible.
</font>
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
<p><h3><a name="s4.5.4">4.5.4 Scan Area Options</a></h3><a name="i119">
<p>The four most important well-known options are the ones that define
the scan area. The scan area is defined by two points (x/y coordinate
pairs) that specify the top-left and the bottom-right corners. This
is illustrated in Figure <a href="doc014.html#f5">5</a>. Note that the origin of the
coordinate system is at the top-left corner of the scan surface as
seen by the sensor (which typically is a mirror image of the scan
surface seen by the user). For this reason, the top-left corner is
the corner for which the abscissa and ordinate values are
simultaneously the <em>smallest</em> and the bottom-right corner is the
corner for which the abscissa and ordinate values are simulatenously
the <em>largest</em>. If this coordinate system is not natural for a
given device, it is the job of the backend to perform the necessary
conversions.
<p><a name="f5"></a>
<center>
<img width=330 height=306 src="img004.gif">
<p><center>Figure 5: Scan area options</center>
</center>
<p>
<p>The names of the four options that define the scan area are given in
the table below:
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>Name</b> </td>
<td colspan=1 align=left nowrap> <b>Description</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>tl-x<a name="i120"></tt> </td>
<td colspan=1 align=left nowrap> Top-left x coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>tl-y<a name="i121"></tt> </td>
<td colspan=1 align=left nowrap> Top-left y coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>br-x<a name="i122"></tt> </td>
<td colspan=1 align=left nowrap> Bottom-right x coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>br-y<a name="i123"></tt> </td>
<td colspan=1 align=left nowrap> Bottom-right y coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
There are several rules that should be followed by front and backends
regarding these options:
<ul>
<p><li>Backends must attach a unit of either pixels
(<tt>SANE_UNIT_PIXEL</tt>) or millimeters (<tt>SANE_UNIT_MM</tt>) to
these options. The unit of all four options must be identical.
<p><li>Whenever meaningful, a backend should attach a range or a
word-list constraint to these options.
<p><li>A frontend can determine the size of the scan surface by first
checking that the options have range constraints associated. If a
range or word-list constraints exist, the frontend can take the
minimum and maximum values of one of the x and y option
range-constraints to determine the scan surface size.
<p><li>A frontend must work properly with any or all of these options
missing.
<font color="darkgreen">
<li>A frontend may temporarily set the values in a way that
<tt>tl-x</tt> is larger than <tt>br-x</tt> and <tt>tl-y</tt> is larger than
<tt>br-y</tt>.
</font>
<p></ul>
<p><h3><a name="s4.5.5">4.5.5 Depth option</a></h3><a name="i124">
<font color="darkgreen">
Option <tt>depth</tt> is used to select the image depth in bits/sample
in multi bit mode - (this means for 24 bit RGB mode this value must be 8).
The type of this option is <tt>SANE_TYPE_INT</tt>.
The unit is <tt>SANE_UNIT_BIT</tt>. For 1 bit modes
(Lineart or Halftone) this option has to be inactive.
For selection of 1 bit modes (Lineart or Halftone) the
backend should use the well-known option <tt>mode</tt>.<br>
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<h3><a name="s4.5.6">4.5.6 Gamma table options</a></h3><a name="i125">
<font color="darkgreen">
The <tt>gamma-table</tt> option defines a <tt>SANE_CONSTRAINT_RANGE</tt>
of the type <tt>SANE_TYPE_INT</tt> which represents the gamma correction
table for gray. In color mode the <tt>gamma-table</tt> may be used to set
a common gamma correction for red, green and blue. The options
<tt>red-gamma-table</tt>, <tt>green-gamma-table</tt> and <tt>blue-gamma-table</tt>
are used in color mode to set a gamma correction for each color
separately. In color mode the backend is free to use only the
<tt>gamma-table</tt> option, only the <tt>red-</tt>, <tt>green-</tt> and
<tt>blue-gamma-table</tt> or all four options. When all four options
are used then the color tables should do a gamma correction with
the same input and output bit depth and the gray gamma table should
reduce (if necessary) the bit depth from the scanner internal
bit depth to the output bit depth. This should e.g. look like this:
<pre>
red_value = gamma-table(red-gamma-table(value))
green_value = gamma-table(green-gamma-table(value))
blue_value = gamma-table(blue-gamma-table(value))
</pre>
<p>The backend should not use the gamma tables to emulate other functions or options
like highlight, shadow, contrast, brightness, threshold, analog_gamma.
These functions are common for all backends and should be added to the frontend
or a meta-backend.<br>
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<h3><a name="s4.5.7">4.5.7 Scan Mode options</a></h3><a name="i126">
<font color="darkgreen">
The option <tt>mode</tt> defines a <tt>SANE_CONSTRAINT_STRING_LIST</tt>
of type <tt>SANE_TYPE_STRING</tt>.
It is used to select the scanmode (e.g. Color or Gray).
Well known modes are: <tt>Color</tt>, <tt>Gray</tt>, <tt>Halftone</tt>
and <tt>Lineart</tt>. <tt>Color</tt> and <tt>Gray</tt> are multi bit
modes (8 or 16 bits/sample), <tt>Halftone</tt> and <tt>Lineart</tt>
are single bit modes.<br>
This way a frontend can select e.g the mode <tt>Gray</tt>
for scanning a fax.<br>
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<h3><a name="s4.5.8">4.5.8 Scan Source options</a></h3><a name="i127">
<font color="darkgreen">
The option <tt>source</tt> is used to select the scan source
(e.g. Automatic Document Feeder).
It defines a <tt>SANE_CONSTRAINT_STRING_LIST</tt>
of type <tt>SANE_TYPE_STRING</tt>.
Well known sources are: <tt>Flatbed</tt>, <tt>Transparancy Adapter</tt> and
<tt>Automatic Document Feeder</tt>.<br>
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<p><h3><a name="s4.5.9">4.5.9 Threshold</a></h3><a name="i128">
<font color="darkgreen">
The option <tt>threshold</tt> is used to define the threshold
for Lineart and maybe Halftone mode. In multi bit modes
this option should be set inactive.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_PERCENT</tt>. The value range
should be 0.0...100.0 if possible.
It defines the minimum intensity to get a white point / full intensity
(image data bit = 0). The backend has to
scale the values in the following way:<br>
A value of 0.0 means all pixels get white /full intensity (all image data
bits are 0). A value of 50.0 means intensities brighter than medium gray
get white / full intensity (bit 0). A value of 100.0 means all pixels get
black (all image data bits are 1). If the scanner is not able to
cover the full range the backend has to define a reduced
value range (e.g. 30...70 percent).
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<p><h3><a name="s4.5.10">4.5.10 Analog gamma</a></h3><a name="i129">
<font color="darkgreen">
The option <tt>analog-gamma</tt> is used to define the gamma value
for an analog gamma function of the scanner in multi bit modes.
In 1 bit modes this option should be set inactive.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_NONE</tt>. The value range
can be defined by the backend as supported. The values
have to be positive. A gamma value of 1.0 means that
the gamma correction has no effect. A value larger than
1.0 increases the brightness of the image.
In color mode there also can be options <tt>analog-gamma-red</tt>,
<tt>analog-gamma-green</tt> and <tt>analog-gamma-blue</tt>.
It is not allowed to emulate an analog gamma function by
a digital gamma table. The backend has to disable (or not
define) this option when the scanner does not support an
analog (hardware) gamma function.
<p>When analog gamma, highlight and shadow functions are available
at the same time then the backend author has to care about the order
in which the functions are implemented in the scanner hardware.
The SANE standard expects that changing the analog gamma value
has no effect on the shadow and highlight function. When the
analog gamma function is executed in the scanner hardware
before the shadow and highlight functions then the backend
should do a compensation. For this the shadow and highlight
values have to be gamma corrected with the relevant analog gamma value.
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<p><h3><a name="s4.5.11">4.5.11 Shadow</a></h3><a name="i130">
<font color="darkgreen">
The option <tt>shadow</tt> is used to define the shadow level / black point level.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_PERCENT</tt>. The value range
should be 0.0...100.0 if possible.
It is used to define the maximum intensity level that creates an image data value
of 0 (black). The backend has to scale the values in the following way:<br>
A value of 0.0 means that the sensitivity range is not reduced, only the
minimum intensity produces an image data value of 0 (black).
A value of 50.0 means that that a medium intensity and everything that is darker
produces an image data value of 0 (black).
A value of 100.0 means the sensitivity range is reduced to 0, all image
data values are 0 (black). If the scanner is not able to
cover the full range the backend has to define a reduced
value range (e.g. 30...70 percent).
In color mode there can be options <tt>shadow-red</tt>, <tt>shadow-green</tt>
and <tt>shadow-blue</tt>, in this case the <tt>shadow</tt> function has to be disabled.
It is not allowed to emulate a shadow function by
a digital gamma table. The backend has to disable (or not
define) this option when the scanner does not support an
analog (hardware) shadow function.
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<p><h3><a name="s4.5.12">4.5.12 Highlight</a></h3><a name="i131">
<font color="darkgreen">
The option <tt>highlight</tt> is used to define the highlight level / white point level.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_PERCENT</tt>. The value range
should be 0.0...100.0 if possible.
It is used to define the minimum intensity level that creates the maximum possible
image data value (white/full intensity). The backend has to scale the values in the
following way:<br>
A value of 0.0 means the sensitivity range is reduced to 0, all image
data have maximum value (white / full intensity).
A value of 50.0 means that a medium intensity and everything that is brighter
produces the maximum possible image data value (white / full intensity).
A value of 100.0 means that the sensitivity range is not reduced, only the
maximum intensity produces an image data with maximum possible value (white / full intensity).
If the scanner is not able to cover the full range the backend has to define a reduced
value range (e.g. 30...70 percent).
In color mode there can be options <tt>highlight-red</tt>, <tt>highlight-green</tt>
and <tt>highlight-blue</tt>, in this case <tt>highlight</tt> has to be disabled.
It is not allowed to emulate a highlight function by
a digital gamma table. The backend has to disable (or not
define) this option when the scanner does not support an
analog (hardware) highlight function.
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.<br>
</font>
<p><h3><a name="s4.5.13">4.5.13 Turn lamp on and off</a></h3><a name="i132"><a name="i133">
<font color="darkgreen">
The option <tt>lamp-on</tt> is used to turn the lamp of the scanner on.
The type of this option is <tt>SANE_TYPE_BUTTON</tt>.
The unit is <tt>SANE_UNIT_NONE</tt>. When the option is set
then the lamp of the scanner is turned on.
<p>The option <tt>lamp-off</tt> is used to turn the lamp of the scanner off.
The type of this option is <tt>SANE_TYPE_BUTTON</tt>.
The unit is <tt>SANE_UNIT_NONE</tt>. When the option is set
then the lamp of the scanner is turned off.
<p>These options are not mandatory, but if a backend does support them, it
must implement them in a manner consistent with the above definition.<br>
</font>
<p><h3><a name="s4.5.14">4.5.14 Scanner buttons</a></h3><a name="i134">
<font color="darkgreen">
Some scanners have buttons which state can be read by the scanner driver.
It is necessary to implement a locking function for the buttons
because it is possible that several frontends try to connect to the
same backend/scanner at the same time. Imagine what could happen
when no locking would be implemented:
Five people have started a scanning application which is connected
via network to the scanner you want to use. You start a frontend,
put a paper to the scanner and press the scan-button on the scanner.
The scanner does scan three times (because three frontends asked the
button status when you pressed the button). For three people the
image is saved to the harddisk, but it is not sure that your
frontend did scan the image.<br>
<p>A backend that does make available the scanner-buttons has to
implement the following options:<br>
<tt>scanner-buttons-lock</tt> is of type <tt>SANE_TYPE_BOOL</tt>, default = <tt>SANE_FALSE</tt><br>
<tt>scanner-buttons-status</tt> is of type <tt>SANE_TYPE_INT</tt>, default = 0<br>
<tt>scanner-buttons-status-update</tt> is of type <tt>SANE_TYPE_BUTTON</tt><br>
When setting these options the backend does not set <tt>SANE_INFO_RELOAD_OPTIONS</tt>
or <tt>SANE_INFO_RELOAD_PARAMS</tt> if not explictly defined.
<p>A frontend has to disable the usage of the scanner-buttons by default. This is important
because other frontends will not be able to use the buttons when the button-functions are locked.
Another important thing is that some scanners do not turn off their lamp when the driver
does frequently talk to the scanner (what is done when reading the button status from the scanner).
<p><ul>
<p><li>
A frontend that wants to read the button status has to lock the
button functions at first. For this it does set the option
<tt>scanner-buttons-lock</tt> to <tt>SANE_TRUE</tt>.
While setting the value of option <tt>scanner-buttons-lock</tt> to <tt>SANE_TRUE</tt>
the backend does check if a lockfile (e.g. "backend"-buttons.lock) does exist.
The lockfile has to be placed in a directory where every user has read and write access to.
<p> <ul>
<li>
If the lockfile does not exist then the backend creates the lockfile and writes the
process ID (PID) of the backend to the file. Button access is allowed: the value
of option <tt>scanner-buttons-lock</tt> is set to <tt>SANE_TRUE</tt>
<li>
If the file does exist and the backend PID is not the file PID then the
backend has to check if the process with the PID stored in the lockfile
still is running. If yes then the button access is not allowed: the value of
option <tt>scanner-buttons-lock</tt> is set to <tt>SANE_FALSE</tt>. If not then the lockfile
is recreated and the PID of the backend is stored in the lockfile, button
access is allowed: the value of option <tt>scanner-buttons-lock</tt> is set to <tt>SANE_TRUE</tt>
</ul>
<p><li>
The frontend does read the value of option <tt>scanner-buttons-lock</tt>. If
it is <tt>SANE_TRUE</tt> then the frontend has access to the scanner buttons.
If it is <tt>SANE_FALSE</tt> then access has been denied.
<p><li>
If the button access is allowed the frontend has to do the following about
once per second (while not scanning):
<ul>
<li>
The frontend does set option <tt>scanner-buttons-status-update</tt>.
The backend checks if access to the buttons is allowed by comparing
the backend PID with the lockfile PID. If access is allowed it
does read the button status from the scanner and stores it in
the option <tt>scanner-buttons-status</tt>, each bit represents a button, a
value of 0 means the button is not pressed, a value of 1 means that the button
is pressed. When the scanner is busy the backend must not wait, it has to
return immedeatly and the button state keeps unchanged.
The backend has to implement a timeout function. When no button has been pressed
within a predefined time (e.g. 15 minutes) then the access permission is lost.
In this case the backend does set option <tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>
and does set <tt>SANE_INFO_RELOAD_OPTIONS</tt> to inform the frontend that it has
lost permission to access the scanner-button functions.
If access is not allowed it does set the <tt>scanner-buttons-status</tt> to 0.
<p> <li>
The frontend does read the value of option <tt>scanner-buttons-status</tt>
</ul>
<p><li>
When the frontend does exit or it does not want to use the buttons
it does set option <tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>.
The backend does check if the backend PID and the lockfile PID are
the same. If this is true then it removes the lockfile and sets the value
of <tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>.
<p><tt>sane_close()</tt> should do the same as setting option
<tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>.
<p></ul>
</font>
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<title>Network Protocol</title>
<h1><a name="s5">5 Network Protocol</a></h1>
<p>The SANE interface has been designed to facilitate network access to
image acquisition devices. In particular, most SANE implementations
are expected to support a network backend (net client) and a
corresponding network daemon (net server) that allows accessing image
acquisition devices through a network connection. Network access is
useful in several situations:
<ul>
<p><li>To provide controlled access to resources that are inaccessible
to a regular user. For example, a user may want to access a device
on a host where she has no account on. With the network protocol,
it is possible to allow certain users to access scanners without
giving them full access to the system.
<p> Controlling access through the network daemon can be useful even in
the local case: for example, certain backends may require root
privileges to access a device. Rather than installing each frontend
as setuid-root, a system administrator could instead install the
SANE network daemon as setuid-root. This enables regular users to
access the privileged device through the SANE daemon (which,
presumably, supports a more fine-grained access control mechanism
than the simple setuid approach). This has the added benefit that
the system administrator only needs to trust the SANE daemon, not
each and every frontend that may need access to the privileged
device.
<p><li>Network access provides a sense of ubiquity of the available
image acquisition devices. For example, in a local area network
environment, this allows a user to log onto any machine and have
convenient access to any resource available to any machine on the
network (subject to permission constraints).
<p><li>For devices that do not require physical access when used (e.g.,
video cameras), network access allows a user to control and use
these devices without being in physical proximity. Indeed, if such
devices are connected to the Internet, access from any place in the
world is possible.
<p></ul>
<p>The network protocol described in this chapter has been design with
the following goals in mind:
<ol>
<p><li>Image transmission should be efficient (have low encoding
overhead).
<p><li>Accessing option descriptors on the client side must be
efficient (since this is a very common operation).
<p><li>Other operations, such as setting or inquiring the value of an
option are less performance critical since they typically require
explicit user action.
<p><li>The network protocol should be simple and easy to implement on
any host architecture and any programming language.
<p></ol>
The SANE protocol can be run across any transport protocol that
provides reliable data delivery. While SANE does not specify a
specific transport protocol, it is expected that TCP/IP will be among
the most commonly used protocols.
<p><h2><a href="doc016.html">5.1 Data Type Encoding</a></h2><h2><a href="doc017.html">5.2 Remote Procedure Call Requests</a></h2><p><hr>
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<title>Data Type Encoding</title>
<h2><a name="s5.1">5.1 Data Type Encoding</a></h2>
<p><h3><a name="s5.1.1">5.1.1 Primitive Data Types</a></h3>
<p>The four primitive types of the SANE standard are encoded as follows:
<dl>
<p><dt><tt>SANE_Byte<a name="i135"></tt>:<dd> A byte is encoded as an 8 bit value.
Since the transport protocol is assumed to be byte-orientd, the bit
order is irrelevant.
<p><dt><tt>SANE_Word<a name="i136"></tt>:<dd> A word is encoded as 4 bytes (32
bits). The bytes are ordered from most-significant to
least-significant byte (big-endian byte-order).
<p><dt><tt>SANE_Char<a name="i137"></tt>:<dd> A character is currently encoded as an 8-bit
ISO LATIN-1 value. An extension to support wider character sets (16 or 32
bits) is planned for the future, but not supported at this point.
<p><dt><tt>SANE_String<a name="i138"></tt>:<dd> A string pointer is encoded as a
<tt>SANE_Char</tt> array. The trailing NUL byte is considered part
of the array and a <tt>NULL</tt> pointer is encoded as a zero-length
array.
<dt><tt>SANE_Handle<a name="i139"></tt>:<dd> A handle is encoded like a word.
The network backend needs to take care of converting these integer
values to the opaque pointer values that are presented to the user
of the network backend. Similarly, the SANE daemon needs to take
care of converting the opaque pointer values it receives from its
backends into 32-bit integers suitable for use for network encoding.
<p><dt><em>enumeration types<a name="i140"></em>:<dd> Enumeration types are encoded
like words.
<p></dl>
<p><h3><a name="s5.1.2">5.1.2 Type Constructors</a></h3>
<p>Closely following the type constructors of the C language, the SANE network
protocol supports the following four constructors:
<dl>
<p><dt><em>pointer<a name="i141"></em>:<dd> A pointer is encoded by a word that indicates
whether the pointer is a NULL-pointer which is then followed by the
value that the pointer points to (in the case of a non-NULL pointer;
in the case of a NULL pointer, no bytes are encoded for the pointer
value).
<p><dt><em>array<a name="i142"></em>:<dd> An array is encoded by a word that indicates
the length of the array followed by the values of the elements in
the array. The length may be zero in which case no bytes are
encoded for the element values.
<p><dt><em>structure<a name="i143"></em>:<dd> A structure is encoded by simply encoding the
structure members in the order in which they appear in the
corresponding C type declaration.
<p><dt><em>union<a name="i144"></em>:<dd> A union must always be accompanied by a tag
value that indicates which of the union members is the currently the
active one. For this reason, the union itself is encoded simply by
encoding the value of the currently active member.
<p></dl>
<p>Note that for type constructors, the pointer, element, or member
values themselves may have a constructed type. Thus, the above rules
should be applied recursively until a sequence of primitive types has
been found.
<p>Also SANE had no need for encoding of circular structures. This
greatly simplifies the network protocol.
<p><p><hr>
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<title>Remote Procedure Call Requests</title>
<h2><a name="s5.2">5.2 Remote Procedure Call Requests</a></h2>
<p>The SANE network protocol is a client/server-style remote procedure
call (RPC) protocol. This means that all activity is initiated by the
client side (the network backend)---a server is restricted to
answering request by the client.
<p><h3><a name="s5.2.1">5.2.1 <tt>SANE_NET_INIT<a name="i145"></tt></a></h3>
<p>This RPC establishes a connection to a particular SANE network daemon.
It must be the first call in a SANE network session. The parameter
and reply arguments for this call are shown in the table below:
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word version_code</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String user_name</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word version_code</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>version_code</tt> argument in the request is the SANE
version-code of the network backend that is contacting the network
daemon (see Section <a href="doc010.html#s4.1">4.1</a>). The
``build-revision'' in the version code is used to hold the network
protocol version. The SANE network daemon receiving such a request
must make sure that the network protocol version corresponds to a
supported version since otherwise the encoding of the network stream
may be incompatible (even though the SANE interface itself may be
compatible). The <tt>user_name</tt> argument is the name of the user
on whose behalf this call is being performed. If the network backend
cannot determine a user-name, it passes a <tt>NULL</tt> pointer for this
argument. No trust should be placed in the authenticity of this
user-name. The intent of this string is to provide more convenience
to the user. E.g., it could be used as the default-user name in
subsequent authentication calls.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values.<a name="F2"><a href="footnotes.html#000002"><sup><fontsize=-2>2</font></sup></a></a> The <tt>version_code</tt> argument returns the
SANE version-code that the network daemon supports. See the comments
in the previous paragraph on the meaning of the build-revision in this
version code.
<p><h3><a name="s5.2.2">5.2.2 <tt>SANE_NET_GET_DEVICES<a name="i147"></tt></a></h3>
<p>This RPC is used to obtain the list of devices accessible by the SANE
daemon.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>void</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Device ***device_list</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
There are no arguments in the request for this call.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values. The <tt>device_list</tt>
argument is a pointer to a <tt>NULL</tt>-terminated array of
<tt>SANE_Device</tt> pointers.
<p><h3><a name="s5.2.3">5.2.3 <tt>SANE_NET_OPEN<a name="i149"></tt></a></h3>
<p>This RPC is used to open a connection to a remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String device_name</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Word handle</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_String resource</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>device_name</tt> argument specifies the name of the device to
open.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values. The <tt>handle</tt>
argument specifies the device handle that uniquely identifies the
connection. The <tt>resource</tt> argument is used to request
authentication. If it has a non-<tt>NULL</tt> value, the network
backend should authenticate the specified resource and then retry this
operation (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
authorize a resource).
<p><h3><a name="s5.2.4">5.2.4 <tt>SANE_NET_CLOSE<a name="i151"></tt></a></h3>
<p>This RPC is used to close a connection to a remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection that should be
closed.
<p>In the reply, the <tt>dummy</tt> argument is unused. Its purpose is to
ensure proper synchronization (without it, a net client would not be
able to determine when the RPC has completed).
<p><h3><a name="s5.2.5">5.2.5 <tt>SANE_NET_GET_OPTION_DESCRIPTORS<a name="i153"></tt></a></h3>
<p>This RPC is used to obtain <em>all</em> the option descriptors for a
remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>Option_Descriptor_Array odesc</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the remote device whose option
descriptors should be obtained.
<p>In the reply, the <tt>odesc</tt> argument is used to return the array of
option descriptors. The option descriptor array has the following
structure:
<blockquote><a name="i155">
<pre>
struct Option_Descriptor_Array
{
SANE_Word num_options;
SANE_Option_Descriptor **desc;
};
</pre>
</blockquote>
<p><h3><a name="s5.2.6">5.2.6 <tt>SANE_NET_CONTROL_OPTION<a name="i156"></tt></a></h3>
<p>This RPC is used to control (inquire, set, or set to automatic) a
specific option of a remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word option</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word info</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word action</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word value_type</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word value_type</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word value_size</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word value_size</tt> </td>
<td colspan=1 align=left nowrap> <tt>void *value</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>void *value</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_String *resource</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the remote device whose option
should be controlled. Argument <tt>option</tt> is the number (index) of
the option that should be controlled. Argument <tt>action</tt>
specifies what action should be taken (get, set, or set automatic).
Argument <tt>value_type</tt> specifies the type of the option value
(must be one of <tt>SANE_TYPE_BOOL</tt>, <tt>SANE_TYPE_INT</tt>,
<tt>SANE_TYPE_FIXED</tt>, <tt>SANE_TYPE_STRING</tt>,
<tt>SANE_TYPE_BUTTON</tt>). Argument <tt>value_size</tt> specifies
the size of the option value in number of bytes (see
Section <a href="doc011.html#s4.2.9.6">4.2.9.6</a> for the precise meaning of this value).
Finally, argument <tt>value</tt> is a pointer to the option value. It
must be a writeable area that is at least <tt>value_size</tt> bytes
large. (Note that this area must be writable even if the action is to
set the option value. This is because the backend may not be able to
set the exact option value, in which case the option value is used to
return the next best value that the backend has chosen.)
<p>In the reply, argument <tt>resource</tt> is set to the name of the
resource that must be authorized before this call can be retried. If
this value is non-<tt>NULL</tt>, all other arguments have undefined
values (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
authorize a resource). Argument <tt>status</tt> indicates the
completion status. If the value is anything other than
<tt>SANE_STATUS_SUCCESS</tt>, the remainder of the reply has undefined
values. The <tt>info</tt> argument returns the information on how well
the backend was able to satisfy the request. For details, see the
description of the corresponding argument in
Section <a href="doc012.html#s4.3.7">4.3.7</a>. Arguments <tt>value_type</tt> and
<tt>value_size</tt> have the same values as the arguments by the same
name in corresponding request. The values are repeated here to ensure
that both the request and the reply are self-contained (i.e., they can
be encoded and decoded independently). Argument <tt>value</tt> is holds
the value of the option that has become effective as a result of this
RPC.
<p><h3><a name="s5.2.7">5.2.7 <tt>SANE_NET_GET_PARAMETERS<a name="i158"></tt></a></h3>
<p>This RPC is used to obtain the scan parameters of a remote SANE
device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Parameters params</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection to the remote
device whose scan parameters should be returned.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values. The argument
<tt>params</tt> is used to return the scan parameters.
<p><h3><a name="s5.2.8">5.2.8 <tt>SANE_NET_START<a name="i160"></tt></a></h3>
<p>This RPC is used to start image acquisition (scanning).
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Word port</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Word byte_order</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_String resource</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection to the remote
device from which the image should be acquired.
<p>In the reply, argument <tt>resource</tt> is set to the name of the
resource that must be authorized before this call can be retried. If
this value is non-<tt>NULL</tt>, all other arguments have undefined
values (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
authorize a resource). Argument, <tt>status</tt> indicates the
completion status. If the value is anything other than
<tt>SANE_STATUS_SUCCESS</tt>, the remainder of the reply has
undefined values. The argument <tt>port</tt> returns the port number
from which the image data will be available. To read the image data,
a network client must connect to the remote host at the indicated port
number. Through this port, the image data is transmitted as a
sequence of data records. Each record starts with the data length in
bytes. The data length is transmitted as a sequence of four bytes.
These bytes should be interpreted as an unsigned integer in big-endian
format. The four length bytes are followed by the number of data
bytes indicated by the length. Except for byte-order, the data is in
the same format as defined for <tt>sane_read()</tt>. Since some
records may contain no data at all, a length value of zero is
perfectly valid. The special length value of <tt>0xffffffff</tt> is
used to indicate the end of the data stream. That is, after receiving
a record length of <tt>0xffffffff</tt>, the network client should close
the data connection and stop reading data.
<p>Argument <tt>byte_order</tt> specifies the byte-order of the image
data. A value of 0x1234 indicates little-endian format, a value of
0x4321 indicates big-endian format. All other values are presently
undefined and reserved for future enhancements of this protocol. The
intent is that a network server sends data in its own byte-order and
the client is responsible for adjusting the byte-order, if necessary.
This approach causes no unnecessary overheads in the case where the
server and client byte-order match and puts the extra burden on the
client side when there is a byte-order mismatch. Putting the burden
on the client-side improves the scalability properties of this
protocol.
<p><h3><a name="s5.2.9">5.2.9 <tt>SANE_NET_CANCEL<a name="i162"></tt></a></h3>
<p>This RPC is used to cancel the current operation of a remote SANE
device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection whose operation
should be cancelled.
<p>In the reply, the <tt>dummy</tt> argument is unused. Its purpose is to
ensure proper synchronization (without it, a net client would not be
able to determine when the RPC has completed).
<p><h3><a name="s5.2.10">5.2.10 <tt>SANE_NET_AUTHORIZE<a name="i164"></tt></a></h3>
<a name="i166">
<p>This RPC is used to pass authorization data from the net client to the
net server.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String resource</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String username</tt> </td>
<td colspan=1 align=left nowrap> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String password</tt> </td>
<td colspan=1 align=left nowrap> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>resource</tt> argument specifies the name of the resource to be
authorized. This argument should be set to the string returned in the
<tt>resource</tt> argument of the RPC reply that required this
authorization call. The <tt>username</tt> and <tt>password</tt> are the
name of the user that is accessing the resource and the password for
the specified resource/user pair.
<p>Since the password is not encrypted during network transmission, it is
recommended to use the following extension:
<p>If the server adds the string `<tt>$MD5$</tt>' to the resource-name followed
by a random string not longer then 128 bytes, the client may answer with the
MD5 digest of the concatenation of the password and the random string. To
differentiate between the MD5 digest and a strange password the client prepends
the MD5 digest with the string `<tt>$MD5$</tt>'.
<p>In the reply, <tt>dummy</tt> is completely unused. Note that there is
no direct failure indication. This is unnecessary since a net client
will retry the RPC that resulted in the authorization request until
that call succeeds (or until the request is cancelled). The RPC that resulted
in the authorization request continues after the reply from the client and may
fail with <tt>SANE_STATUS_ACCESS_DENIED</tt>.
<p><h3><a name="s5.2.11">5.2.11 <tt>SANE_NET_EXIT<a name="i167"></tt></a></h3>
<p>This RPC is used to disconnect a net client from a net server. There
are no request or reply arguments in this call. As a result of this
call, the connection between the client and the server that was
established by the <tt>SANE_NET_INIT</tt> call will be closed.
<p>
<p><p><hr>
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<hr>
<title>Contact Information</title>
<h1><a name="s6">6 Contact Information</a></h1>
<p>The SANE standard is discussed and evolved via a mailing list.
Anybody with email access to the Internet can automatically join and
leave the discussion group by sending mail to the following address.
<blockquote><a name="i169">
<pre>
majordomo@mostang.com
</pre>
</blockquote>
To subscribe, send a mail with the body ``<tt>subscribe sane-devel</tt>'' to the
above address.
<p>A complete list of commands supported can be obtained by sending a
mail with a subject of ``<tt>help</tt>'' to the above address. The
mailing list is archived and available through the SANE home page at
URL:
<blockquote>
<a href="http://www.mostang.com/sane/">http://www.mostang.com/sane/</a>
</blockquote>
<p>
<p>
<p><hr>
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<hr>
<h1>Index</h1>
<p><multicol cols=2>
<p><a href="doc014.html#i129">analog gamma option</a><br>
<a href="doc016.html#i142">array</a><br>
<p><a href="doc014.html#i124">bit depth option</a><br>
<a href="doc014.html#i122">br-x</a><br>
<a href="doc014.html#i123">br-y</a><br>
<p><a href="doc013.html#i113">code flow</a><br>
<p><a href="doc011.html#i43">device-name</a><br>
<a href="doc012.html#i80">domain</a><br>
<p><a href="doc016.html#i140">enumeration types</a><br>
<p><a href="doc014.html#i125">gamma table options</a><br>
<p><a href="doc014.html#i131">hightlight options</a><br>
<p><a href="doc008.html#i0">image data format</a><br>
<p><a href="doc014.html#i133">lamp-off option</a><br>
<a href="doc014.html#i132">lamp-on option</a><br>
<p><a href="doc018.html#i169">mailing list</a><br>
<a href="doc014.html#i126">mode options</a><br>
<p><a href="doc017.html#i166">network authorization</a><br>
<a href="doc011.html#i26">NUL</a><br>
<p><a href="doc014.html#i115">option count</a><br>
<a href="doc017.html#i155">Option_Descriptor_Array</a><br>
<p><a href="doc012.html#i82">password</a><br>
<a href="doc016.html#i141">pointer</a><br>
<a href="doc014.html#i118">preview mode</a><br>
<p><a href="doc014.html#i117">resolution option</a><br>
<p><a href="doc012.html#i89">SANE_Action</a><br>
<a href="doc012.html#i90">SANE_ACTION_GET_VALUE</a><br>
<a href="doc012.html#i92">SANE_ACTION_SET_AUTO</a><br>
<a href="doc012.html#i91">SANE_ACTION_SET_VALUE</a><br>
<a href="doc012.html#i79">SANE_Authorization_Callback</a><br>
<a href="doc011.html#i16">SANE_Bool</a><br>
<a href="doc011.html#i14">SANE_Byte</a><br>
<a href="doc016.html#i135">SANE_Byte</a><br>
<a href="doc012.html#i109">sane_cancel</a><br>
<a href="doc011.html#i70">SANE_CAP_ADVANCED</a><br>
<a href="doc011.html#i68">SANE_CAP_AUTOMATIC</a><br>
<a href="doc011.html#i67">SANE_CAP_EMULATED</a><br>
<a href="doc011.html#i65">SANE_CAP_HARD_SELECT</a><br>
<a href="doc011.html#i69">SANE_CAP_INACTIVE</a><br>
<a href="doc011.html#i66">SANE_CAP_SOFT_DETECT</a><br>
<a href="doc011.html#i64">SANE_CAP_SOFT_SELECT</a><br>
<a href="doc011.html#i24">SANE_Char</a><br>
<a href="doc016.html#i137">SANE_Char</a><br>
<a href="doc012.html#i86">sane_close</a><br>
<a href="doc011.html#i72">SANE_CONSTRAINT_NONE</a><br>
<a href="doc011.html#i73">SANE_CONSTRAINT_RANGE</a><br>
<a href="doc011.html#i76">SANE_CONSTRAINT_STRING_LIST</a><br>
<a href="doc011.html#i71">SANE_Constraint_Type</a><br>
<a href="doc011.html#i75">SANE_CONSTRAINT_WORD_LIST</a><br>
<a href="doc012.html#i88">sane_control_option</a><br>
<a href="doc010.html#i11">SANE_CURRENT_MAJOR</a><br>
<a href="doc011.html#i42">SANE_Device</a><br>
<a href="doc012.html#i83">sane_exit</a><br>
<a href="doc011.html#i17">SANE_FALSE</a><br>
<a href="doc011.html#i22">SANE_FIX</a><br>
<a href="doc011.html#i20">SANE_Fixed</a><br>
<a href="doc011.html#i21">SANE_FIXED_SCALE_SHIFT</a><br>
<a href="doc012.html#i98">SANE_Frame</a><br>
<a href="doc008.html#i7">SANE_FRAME_BLUE</a><br>
<a href="doc012.html#i103">SANE_FRAME_BLUE</a><br>
<a href="doc008.html#i3">SANE_FRAME_GRAY</a><br>
<a href="doc012.html#i99">SANE_FRAME_GRAY</a><br>
<a href="doc008.html#i6">SANE_FRAME_GREEN</a><br>
<a href="doc012.html#i102">SANE_FRAME_GREEN</a><br>
<a href="doc008.html#i2">SANE_FRAME_MIME</a><br>
<a href="doc008.html#i10">SANE_FRAME_MIME</a><br>
<a href="doc012.html#i105">SANE_FRAME_MIME</a><br>
<a href="doc008.html#i1">SANE_FRAME_RAW</a><br>
<a href="doc008.html#i8">SANE_FRAME_RAW</a><br>
<a href="doc008.html#i9">SANE_FRAME_RAW</a><br>
<a href="doc012.html#i104">SANE_FRAME_RAW</a><br>
<a href="doc008.html#i5">SANE_FRAME_RED</a><br>
<a href="doc012.html#i101">SANE_FRAME_RED</a><br>
<a href="doc008.html#i4">SANE_FRAME_RGB</a><br>
<a href="doc012.html#i100">SANE_FRAME_RGB</a><br>
<a href="doc012.html#i84">sane_get_devices</a><br>
<a href="doc012.html#i87">sane_get_option_descriptor</a><br>
<a href="doc012.html#i96">sane_get_parameters</a><br>
<a href="doc012.html#i111">sane_get_select_fd</a><br>
<a href="doc011.html#i28">SANE_Handle</a><br>
<a href="doc016.html#i139">SANE_Handle</a><br>
<a href="doc012.html#i93">SANE_INFO_INEXACT</a><br>
<a href="doc012.html#i94">SANE_INFO_RELOAD_OPTIONS</a><br>
<a href="doc012.html#i107">SANE_INFO_RELOAD_OPTIONS</a><br>
<a href="doc012.html#i95">SANE_INFO_RELOAD_PARAMS</a><br>
<a href="doc012.html#i78">sane_init</a><br>
<a href="doc011.html#i19">SANE_Int</a><br>
<a href="doc017.html#i164">SANE_NET_AUTHORIZE</a><br>
<a href="doc017.html#i165">SANE_NET_AUTHORIZE</a><br>
<a href="doc017.html#i162">SANE_NET_CANCEL</a><br>
<a href="doc017.html#i163">SANE_NET_CANCEL</a><br>
<a href="doc017.html#i151">SANE_NET_CLOSE</a><br>
<a href="doc017.html#i152">SANE_NET_CLOSE</a><br>
<a href="doc017.html#i156">SANE_NET_CONTROL_OPTION</a><br>
<a href="doc017.html#i157">SANE_NET_CONTROL_OPTION</a><br>
<a href="doc017.html#i167">SANE_NET_EXIT</a><br>
<a href="doc017.html#i168">SANE_NET_EXIT</a><br>
<a href="doc017.html#i147">SANE_NET_GET_DEVICES</a><br>
<a href="doc017.html#i148">SANE_NET_GET_DEVICES</a><br>
<a href="doc017.html#i153">SANE_NET_GET_OPTION_DESCRIPTORS</a><br>
<a href="doc017.html#i154">SANE_NET_GET_OPTION_DESCRIPTORS</a><br>
<a href="doc017.html#i158">SANE_NET_GET_PARAMETERS</a><br>
<a href="doc017.html#i159">SANE_NET_GET_PARAMETERS</a><br>
<a href="doc017.html#i145">SANE_NET_INIT</a><br>
<a href="doc017.html#i146">SANE_NET_INIT</a><br>
<a href="doc017.html#i149">SANE_NET_OPEN</a><br>
<a href="doc017.html#i150">SANE_NET_OPEN</a><br>
<a href="doc017.html#i160">SANE_NET_START</a><br>
<a href="doc017.html#i161">SANE_NET_START</a><br>
<a href="doc012.html#i85">sane_open</a><br>
<a href="doc011.html#i46">SANE_Option_Descriptor</a><br>
<a href="doc011.html#i62">SANE_OPTION_IS_ACTIVE</a><br>
<a href="doc011.html#i63">SANE_OPTION_IS_SETTABLE</a><br>
<a href="doc012.html#i97">SANE_Parameters</a><br>
<a href="doc011.html#i74">SANE_Range</a><br>
<a href="doc012.html#i108">sane_read</a><br>
<a href="doc012.html#i110">sane_set_io_mode</a><br>
<a href="doc012.html#i106">sane_start</a><br>
<a href="doc011.html#i29">SANE_Status</a><br>
<a href="doc011.html#i41">SANE_STATUS_ACCESS_DENIED</a><br>
<a href="doc011.html#i32">SANE_STATUS_CANCELLED</a><br>
<a href="doc011.html#i38">SANE_STATUS_COVER_OPEN</a><br>
<a href="doc011.html#i33">SANE_STATUS_DEVICE_BUSY</a><br>
<a href="doc011.html#i35">SANE_STATUS_EOF</a><br>
<a href="doc011.html#i30">SANE_STATUS_GOOD</a><br>
<a href="doc012.html#i77">SANE_STATUS_GOOD</a><br>
<a href="doc011.html#i34">SANE_STATUS_INVAL</a><br>
<a href="doc011.html#i39">SANE_STATUS_IO_ERROR</a><br>
<a href="doc011.html#i36">SANE_STATUS_JAMMED</a><br>
<a href="doc011.html#i37">SANE_STATUS_NO_DOCS</a><br>
<a href="doc011.html#i40">SANE_STATUS_NO_MEM</a><br>
<a href="doc011.html#i31">SANE_STATUS_UNSUPPORTED</a><br>
<a href="doc011.html#i25">SANE_String</a><br>
<a href="doc016.html#i138">SANE_String</a><br>
<a href="doc011.html#i27">SANE_String_Const</a><br>
<a href="doc012.html#i112">sane_strstatus</a><br>
<a href="doc011.html#i18">SANE_TRUE</a><br>
<a href="doc011.html#i48">SANE_TYPE_BOOL</a><br>
<a href="doc011.html#i52">SANE_TYPE_BUTTON</a><br>
<a href="doc011.html#i50">SANE_TYPE_FIXED</a><br>
<a href="doc011.html#i53">SANE_TYPE_GROUP</a><br>
<a href="doc011.html#i49">SANE_TYPE_INT</a><br>
<a href="doc011.html#i51">SANE_TYPE_STRING</a><br>
<a href="doc011.html#i54">SANE_Unit</a><br>
<a href="doc011.html#i23">SANE_UNFIX</a><br>
<a href="doc011.html#i57">SANE_UNIT_BIT</a><br>
<a href="doc011.html#i59">SANE_UNIT_DPI</a><br>
<a href="doc011.html#i61">SANE_UNIT_MICROSECOND</a><br>
<a href="doc011.html#i58">SANE_UNIT_MM</a><br>
<a href="doc011.html#i55">SANE_UNIT_NONE</a><br>
<a href="doc011.html#i60">SANE_UNIT_PERCENT</a><br>
<a href="doc011.html#i56">SANE_UNIT_PIXEL</a><br>
<a href="doc011.html#i47">SANE_Value_Type</a><br>
<a href="doc010.html#i12">SANE_VERSION_CODE</a><br>
<a href="doc010.html#i13">SANE_VERSION_MAJOR</a><br>
<a href="doc011.html#i15">SANE_Word</a><br>
<a href="doc016.html#i136">SANE_Word</a><br>
<a href="doc014.html#i119">scan area options</a><br>
<a href="doc014.html#i116">scan resolution</a><br>
<a href="doc014.html#i134">scanner button options</a><br>
<a href="doc014.html#i130">shadow options</a><br>
<a href="doc014.html#i127">source options</a><br>
<a href="doc016.html#i143">structure</a><br>
<p><a href="doc014.html#i128">threshold option</a><br>
<a href="doc014.html#i120">tl-x</a><br>
<a href="doc014.html#i121">tl-y</a><br>
<a href="doc011.html#i45">Type Strings</a><br>
<p><a href="doc016.html#i144">union</a><br>
<a href="doc012.html#i81">username</a><br>
<p><a href="doc011.html#i44">Vendor Strings</a><br>
<p><a href="doc014.html#i114">well-known options</a><br>
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<title>Footnotes</title><h1>Footnotes</h1><p>
<hr><p><b><a href="doc011.html#F1">1</a></b> This is different from ANSI C where
any non-zero integer value represents logical TRUE.
<hr><p><b><a href="doc017.html#F2">2</a></b> The sane network
daemon should be careful not to leak information in the undefined
portion of the reply.

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<html><body>
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<title>./sane</title>
<p>
<p>
<p>
<p>
<p>
<p>
<p>
<p><center><h1><font size=+4>SANE Standard Version 2.0 proposal 0.07 - rauch/beck</font></h1></center>
<center></center>
<center>Dec 5, 2002</center>
<p>
<p><h1><a href="doc002.html">1 Preface</a></h1><h1><a href="doc004.html">2 Introduction</a></h1><h1><a href="doc006.html">3 The SANE Environment</a></h1><h1><a href="doc009.html">4 The SANE Application Programmer Interface (API)</a></h1><h1><a href="doc015.html">5 Network Protocol</a></h1><h1><a href="doc018.html">6 Contact Information</a></h1><p><hr>
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<html><body>
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<a href="doc019.html"><img src=../icons/index.gif alt="Index"></a>
<hr>
<title>Contents</title>
<h1>Contents</h1><p>
<table>
<tr></tr><tr><td colspan=20>1<tt> </tt><a href="doc002.html#s1"><b>Preface</b></a></td></tr>
<tr><td></td><td colspan=20>1.1<tt> </tt><a href="doc003.html#s1.1">About This Document</a></td></tr>
<tr><td></td><td></td><td colspan=20>1.1.1<tt> </tt><a href="doc003.html#s1.1.1">Typographic Conventions</a></td></tr>
<tr></tr><tr><td colspan=20>2<tt> </tt><a href="doc004.html#s2"><b>Introduction</b></a></td></tr>
<tr><td></td><td colspan=20>2.1<tt> </tt><a href="doc005.html#s2.1">Terminology</a></td></tr>
<tr></tr><tr><td colspan=20>3<tt> </tt><a href="doc006.html#s3"><b>The SANE Environment</b></a></td></tr>
<tr><td></td><td colspan=20>3.1<tt> </tt><a href="doc007.html#s3.1">Attaching to a SANE backend</a></td></tr>
<tr><td></td><td colspan=20>3.2<tt> </tt><a href="doc008.html#s3.2">Image Data Format</a></td></tr>
<tr><td></td><td></td><td colspan=20>3.2.1<tt> </tt><a href="doc008.html#s3.2.1">Pixel oriented frames</a></td></tr>
<tr><td></td><td></td><td colspan=20>3.2.2<tt> </tt><a href="doc008.html#s3.2.2">Arbitrary data frames</a></td></tr>
<tr></tr><tr><td colspan=20>4<tt> </tt><a href="doc009.html#s4"><b>The SANE Application Programmer Interface (API)</b></a></td></tr>
<tr><td></td><td colspan=20>4.1<tt> </tt><a href="doc010.html#s4.1">Version Control</a></td></tr>
<tr><td></td><td colspan=20>4.2<tt> </tt><a href="doc011.html#s4.2">Data Types</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.1<tt> </tt><a href="doc011.html#s4.2.1">Base Types</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.2<tt> </tt><a href="doc011.html#s4.2.2">Boolean Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.3<tt> </tt><a href="doc011.html#s4.2.3">Integer Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.4<tt> </tt><a href="doc011.html#s4.2.4">Fixed-point Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.5<tt> </tt><a href="doc011.html#s4.2.5">Text</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.5.1<tt> </tt><a href="doc011.html#s4.2.5.1">Character Type</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.5.2<tt> </tt><a href="doc011.html#s4.2.5.2">String Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.6<tt> </tt><a href="doc011.html#s4.2.6">Scanner Handle Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.7<tt> </tt><a href="doc011.html#s4.2.7">Status Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.8<tt> </tt><a href="doc011.html#s4.2.8">Device Descriptor Type</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.9<tt> </tt><a href="doc011.html#s4.2.9">Option Descriptor Type</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.1<tt> </tt><a href="doc011.html#s4.2.9.1">Option Name</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.2<tt> </tt><a href="doc011.html#s4.2.9.2">Option Title</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.3<tt> </tt><a href="doc011.html#s4.2.9.3">Option Description</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.4<tt> </tt><a href="doc011.html#s4.2.9.4">Option Value Type</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.5<tt> </tt><a href="doc011.html#s4.2.9.5">Option Value Unit</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.6<tt> </tt><a href="doc011.html#s4.2.9.6">Option Value Size</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.7<tt> </tt><a href="doc011.html#s4.2.9.7">Option Capabilities</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.9.8<tt> </tt><a href="doc011.html#s4.2.9.8">Option Value Constraints</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.2.10<tt> </tt><a href="doc011.html#s4.2.10">Internationalization</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.10.1<tt> </tt><a href="doc011.html#s4.2.10.1">How is a text marked for translation</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.10.2<tt> </tt><a href="doc011.html#s4.2.10.2">Which texts shall be marked for translation?</a></td></tr>
<tr><td></td><td></td><td></td><td colspan=20>4.2.10.3<tt> </tt><a href="doc011.html#s4.2.10.3">File formats and translation functions</a></td></tr>
<tr><td></td><td colspan=20>4.3<tt> </tt><a href="doc012.html#s4.3">Operations</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.1<tt> </tt><a href="doc012.html#s4.3.1"><tt>sane_init</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.2<tt> </tt><a href="doc012.html#s4.3.2"><tt>sane_exit</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.3<tt> </tt><a href="doc012.html#s4.3.3"><tt>sane_get_devices</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.4<tt> </tt><a href="doc012.html#s4.3.4"><tt>sane_open</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.5<tt> </tt><a href="doc012.html#s4.3.5"><tt>sane_close</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.6<tt> </tt><a href="doc012.html#s4.3.6"><tt>sane_get_option_descriptor</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.7<tt> </tt><a href="doc012.html#s4.3.7"><tt>sane_control_option</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.8<tt> </tt><a href="doc012.html#s4.3.8"><tt>sane_get_parameters</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.9<tt> </tt><a href="doc012.html#s4.3.9"><tt>sane_start</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.10<tt> </tt><a href="doc012.html#s4.3.10"><tt>sane_read</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.11<tt> </tt><a href="doc012.html#s4.3.11"><tt>sane_cancel</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.12<tt> </tt><a href="doc012.html#s4.3.12"><tt>sane_set_io_mode</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.13<tt> </tt><a href="doc012.html#s4.3.13"><tt>sane_get_select_fd</tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>4.3.14<tt> </tt><a href="doc012.html#s4.3.14"><tt>sane_strstatus</tt></a></td></tr>
<tr><td></td><td colspan=20>4.4<tt> </tt><a href="doc013.html#s4.4">Code Flow</a></td></tr>
<tr><td></td><td colspan=20>4.5<tt> </tt><a href="doc014.html#s4.5">Well-Known Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.1<tt> </tt><a href="doc014.html#s4.5.1">Option Number Count</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.2<tt> </tt><a href="doc014.html#s4.5.2">Scan Resolution Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.3<tt> </tt><a href="doc014.html#s4.5.3">Preview Mode Option</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.4<tt> </tt><a href="doc014.html#s4.5.4">Scan Area Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.5<tt> </tt><a href="doc014.html#s4.5.5">Depth Option</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.6<tt> </tt><a href="doc014.html#s4.5.6">Scan Mode Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.7<tt> </tt><a href="doc014.html#s4.5.7">Scan Source Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.8<tt> </tt><a href="doc014.html#s4.5.8">Threshold Option</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.9<tt> </tt><a href="doc014.html#s4.5.9">Gamma Table Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.10<tt> </tt><a href="doc014.html#s4.5.10">Analog Gamma</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.11<tt> </tt><a href="doc014.html#s4.5.11">Shadow Option</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.12<tt> </tt><a href="doc014.html#s4.5.12">Highlight Option</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.13<tt> </tt><a href="doc014.html#s4.5.13">Lamp Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.14<tt> </tt><a href="doc014.html#s4.5.14">Scanner Button Options</a></td></tr>
<tr><td></td><td></td><td colspan=20>4.5.15<tt> </tt><a href="doc014.html#s4.5.15">Batch Scan Options</a></td></tr>
<tr></tr><tr><td colspan=20>5<tt> </tt><a href="doc015.html#s5"><b>Network Protocol</b></a></td></tr>
<tr><td></td><td colspan=20>5.1<tt> </tt><a href="doc016.html#s5.1">Data Type Encoding</a></td></tr>
<tr><td></td><td></td><td colspan=20>5.1.1<tt> </tt><a href="doc016.html#s5.1.1">Primitive Data Types</a></td></tr>
<tr><td></td><td></td><td colspan=20>5.1.2<tt> </tt><a href="doc016.html#s5.1.2">Type Constructors</a></td></tr>
<tr><td></td><td colspan=20>5.2<tt> </tt><a href="doc017.html#s5.2">Remote Procedure Call Requests</a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.1<tt> </tt><a href="doc017.html#s5.2.1"><tt>SANE_NET_INIT<a name="i151"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.2<tt> </tt><a href="doc017.html#s5.2.2"><tt>SANE_NET_GET_DEVICES<a name="i153"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.3<tt> </tt><a href="doc017.html#s5.2.3"><tt>SANE_NET_OPEN<a name="i155"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.4<tt> </tt><a href="doc017.html#s5.2.4"><tt>SANE_NET_CLOSE<a name="i157"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.5<tt> </tt><a href="doc017.html#s5.2.5"><tt>SANE_NET_GET_OPTION_DESCRIPTORS<a name="i159"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.6<tt> </tt><a href="doc017.html#s5.2.6"><tt>SANE_NET_CONTROL_OPTION<a name="i162"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.7<tt> </tt><a href="doc017.html#s5.2.7"><tt>SANE_NET_GET_PARAMETERS<a name="i164"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.8<tt> </tt><a href="doc017.html#s5.2.8"><tt>SANE_NET_START<a name="i166"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.9<tt> </tt><a href="doc017.html#s5.2.9"><tt>SANE_NET_CANCEL<a name="i168"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.10<tt> </tt><a href="doc017.html#s5.2.10"><tt>SANE_NET_AUTHORIZE<a name="i170"></tt></a></td></tr>
<tr><td></td><td></td><td colspan=20>5.2.11<tt> </tt><a href="doc017.html#s5.2.11"><tt>SANE_NET_EXIT<a name="i173"></tt></a></td></tr>
<tr></tr><tr><td colspan=20>6<tt> </tt><a href="doc018.html#s6"><b>Contact Information</b></a></td></tr>
</table>
<h1>List of Figures</h1>
<table>
<tr><td>1</td><td><a href="doc007.html#f1">Example SANE Hiearchy</a></td></tr>
<tr><td>2</td><td><a href="doc008.html#f2">Transfer order of image data bytes</a></td></tr>
<tr><td>3</td><td><a href="doc008.html#f3">Bit and byte order of image data</a></td></tr>
<tr><td>4</td><td><a href="doc013.html#f4">Code flow</a></td></tr>
<tr><td>5</td><td><a href="doc014.html#f5">Scan area options</a></td></tr>
</table>
<h1>List of Tables</h1>
<table>
<tr><td>1</td><td><a href="doc011.html#f1">Status Codes</a></td></tr>
<tr><td>2</td><td><a href="doc011.html#f2">Predefined Device Information Strings</a></td></tr>
<tr><td>3</td><td><a href="doc011.html#f3">Option Value Types (<tt>SANE_Value_Type</tt>)</a></td></tr>
<tr><td>4</td><td><a href="doc011.html#f4">Physical Units (<tt>SANE_Unit</tt>)</a></td></tr>
<tr><td>5</td><td><a href="doc011.html#f5">Option Capabilities</a></td></tr>
<tr><td>6</td><td><a href="doc011.html#f6">Option Value Constraints</a></td></tr>
<tr><td>7</td><td><a href="doc012.html#f7">Action Values (<tt>SANE_Action</tt>)</a></td></tr>
<tr><td>8</td><td><a href="doc012.html#f8">Additional Information Returned When Setting an Option</a></td></tr>
<tr><td>9</td><td><a href="doc012.html#f9">Frame Format (<tt>SANE_Frame</tt>)</a></td></tr>
</table>
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<title>./sane</title>
<p>
<p>
<p>
<p>
<p>
<p>
<p>
<p><center><h1><font size=+4>SANE Standard Version 2.0 proposal 0.08 - rauch/beck</font></h1></center>
<center></center>
<center>Dec 8, 2002</center>
<p>
<p><h1><a href="doc002.html">1 Preface</a></h1><h1><a href="doc004.html">2 Introduction</a></h1><h1><a href="doc006.html">3 The SANE Environment</a></h1><h1><a href="doc009.html">4 The SANE Application Programmer Interface (API)</a></h1><h1><a href="doc015.html">5 Network Protocol</a></h1><h1><a href="doc018.html">6 Contact Information</a></h1><p><hr>
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<title>Preface</title>
<h1><a name="s1">1 Preface</a></h1>
<p>The SANE standard is being developed by a group of free-software
developers. The process is open to the public and comments as well as
suggestions for improvements are welcome. Information on how to join
the SANE development process can be found in Chapter
<a href="doc018.html#s6">6</a>.
<p>The SANE standard is intended to streamline software development by
providing a standard application programming interface to access
raster scanner hardware. This should reduce the number of different
driver implementations, thereby reducing the need for reimplementing
similar code.
<p><h2><a href="doc003.html">1.1 About This Document</a></h2><p><hr>
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<title>About This Document</title>
<h2><a name="s1.1">1.1 About This Document</a></h2>
<p>This document is intended for developers who are creating either an
application that requires access to raster scanner hardware and for
developers who are implementing a SANE driver. It does not cover
specific implementations of SANE components. Its sole purpose is to
describe and define the SANE application interface that will enable
any application on any platform to interoperate with any SANE backend
for that platform.
<p>The remainder of this document is organized as follows.
Chapter <a href="doc004.html#s2">2</a> provides introductional material.
Chapter <a href="doc006.html#s3">3</a> presents the environment SANE is designed
for. Chapter <a href="doc009.html#s4">4</a> details the SANE Application Programmer
Interface. Chapter <a href="doc015.html#s5">5</a> specifies the network protocol that
can be used to implement the SANE API in a network transparent
fashion. Finally, Chapter <a href="doc018.html#s6">6</a> gives information on how
to join the SANE development process.
<p><h3><a name="s1.1.1">1.1.1 Typographic Conventions</a></h3>
<p>Changes since the last revision of this document are highlighted
like this:
<p><font color="darkgreen">
Paragraphs that changed since the last revision of the documention
are marked like this paragraph.
</font>
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<hr>
<title>Introduction</title>
<h1><a name="s2">2 Introduction</a></h1>
<p>SANE is an application programming interface (API) that provides
standardized access to any raster image scanner hardware. The
standardized interface allows to write just one driver for each
scanner device instead of one driver for each scanner and application.
The reduction in the number of required drivers provides significant
savings in development time. More importantly, SANE raises the level
at which applications can work. As such, it will enable applications
that were previously unheard of in the UNIX world. While SANE is
primarily targeted at a UNIX environment, the standard has been
carefully designed to make it possible to implement the API on
virtually any hardware or operating system.
<p>SANE is an acronym for ``Scanner Access Now Easy.'' Also, the hope is
that SANE is sane in the sense that it will allow easy implementation
of the API while accommodating all features required by today's
scanner hardware and applications. Specifically, SANE should be broad
enough to accommodate devices such as scanners, digital still and
video cameras, as well as virtual devices like image file filters.
<p><h2><a href="doc005.html">2.1 Terminology</a></h2><p><hr>
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<title>Terminology</title>
<h2><a name="s2.1">2.1 Terminology</a></h2>
<p>An application that uses the SANE interface is called a SANE <em>
frontend</em>. A driver that implements the SANE interface is called a
SANE <em>backend</em>. A <em>meta backend</em> provides some means to
manage one or more other backends.
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<title>The SANE Environment</title>
<h1><a name="s3">3 The SANE Environment</a></h1>
<p>SANE is defined as a C-callable library interface. Accessing a raster
scanner device typically consists of two phases: first, various
controls of the scanner need to be setup or queried. In the second
phase, one or more images are acquired.
<p>Since the device controls are widely different from device to device,
SANE provides a generic interface that makes it easy for a frontend to
give a user access to all controls without having to understand each
and every device control. The design principle used here is to
abstract each device control into a SANE <em>option</em>. An option is
a self-describing name/value pair. For example, the brightness
control of a camera might be represented by an option called
<tt>brightness</tt> whose value is an integer in the range from 0 to
255.
<p>With self-describing options, a backend need not be concerned with
<em>presentation</em> issues: the backend simply provides a list of
options that describe all the controls available in the device.
Similarly, there are benefits to the frontend: it need not be
concerned with the <em>meaning</em> of each option. It simply provides
means to present and alter the options defined by the backend.
<p><h2><a href="doc007.html">3.1 Attaching to a SANE backend</a></h2><h2><a href="doc008.html">3.2 Image Data Format</a></h2><p><hr>
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<title>Attaching to a SANE backend</title>
<h2><a name="s3.1">3.1 Attaching to a SANE backend</a></h2>
<p>The process through which a SANE frontend connects to a backend is
platform dependent. Several possibilities exist:
<ul>
<p><li><b>Static linking:</b> A SANE backend may be linked directly into
a frontend. While the simplest method of attaching to a backend, it
is somewhat limited in functionality since the available devices is
limited to the ones for which support has been linked in when the
frontend was built. But even so static linking can be quite useful,
particularly when combined with a backend that can access scanners
via a network. Also, it is possible to support multiple backends
simultaneously by implementing a meta backend that manages several
backends that have been compiled in such a manner that they export
unique function names. For example, a backend called <tt>be</tt>
would normally export a function called <tt>sane_read()</tt>. If
each backend would provide such a function, static linking would
fail due to multiple conflicting definitions of the same symbol.
This can be resolved by having backend <tt>be</tt> include a
header file that has lines of the form:
<blockquote>
<pre>
#define sane_read be_sane_read
</pre>
</blockquote>
With definitions of this kind, backend <tt>be</tt> will export
function name <tt>be_sane_read()</tt>. Thus, all backends will
export unique names. As long as a meta backend knows about these
names, it is possible to combine several backends at link time and
select and use them dynamically at runtime.
<p><li><b>Dynamic linking:</b> A simpler yet more powerful way to
support multiple backends is to exploit dynamic linking on platforms
that support it. In this case, a frontend is linked against a
shared library that implements any SANE backend. Since each
dynamically linked backend exports the same set of global symbols
(all starting with the prefix <tt>sane_</tt>), the dynamic library
that gets loaded at runtime does not necessarily have to be the same
one as one the frontend got linked against. In other words, it is
possible to switch the backend by installing the appropriate backend
dynamic library.
<p> More importantly, dynamic linking makes it easy to implement a meta
backend that loads other backends <em>on demand</em>. This is a
powerful mechanism since it allows adding new backends merely by
installing a shared library and updating a configuration file.
<p><li><b>Network connection:</b> Arguably the ultimate way to attach to
a scanner is by using the network to connect to a backend on a
remote machine. This makes it possible to scan images from any host
in the universe, as long as there is a network connection to that
host and provided the user is permitted to access that scanner.
<p></ul>
<p><p><a name="f1"></a>
<center>
<img width=780 height=384 src="img000.gif">
<p><center>Figure 1: Example SANE Hiearchy</center>
</center>
<p>
<p>The above discussion lists just a few ways for frontends to attach to
a backend. It is of course possible to combine these solutions to
provide an entire hierarchy of SANE backends. Such a hierarchy is
depicted in Figure <a href="doc007.html#f1">1</a>. The figure shows that machine
A uses a dynamic-linking based meta backend called <tt>dll</tt> to
access the backends called <tt>pnm</tt>, <tt>mustek</tt>, and <tt>net</tt>.
The first two are real backends, whereas the last one is a meta
backend that provides network transparent access to remote scanners.
In the figure, machine B provides non-local access to its scanners
through the SANE frontend called <tt>saned</tt>. The <tt>saned</tt> in
turn has access to the <tt>hp</tt> and <tt>autolum</tt> backends through
another instance of the <tt>dll</tt> backend. The <tt>autolum</tt> meta
backend is used to automatically adjust the luminance (brightness) of
the image data acquired by the camera backend called <tt>qcam</tt>.
<p>Note that a meta backend really is both a frontend and a backend at
the same time. It is a frontend from the viewpoint of the backends
that it manages and a backend from the viewpoint of the frontends that
access it. The name ``meta backend'' was chosen primarily because the
SANE standard describes the interface from the viewpoint of a (real)
frontend.
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<title>Image Data Format</title>
<h2><a name="s3.2">3.2 Image Data Format</a></h2><a name="i0">
<p>Arguably the most important aspect of an image acquisition system is how
images are represented. The SANE approach is to define a simple yet powerful
representation that is sufficient for vast majority of applications and
devices. While the representation is simple, the interface has been defined
carefully to allow extending it in the future without breaking backwards
compatibility. Thus, it will be possible to accommodate future applications or
devices that were not anticipated at the time this standard was created.
<p>A SANE image is a rectangular area. The rectangular area is subdivided into a
number of rows and columns. At the intersection of each row and column is a
(preferable quadratic) pixel. A pixel consists of one or more sample values.
Each sample value represents one channel (e.g., the red channel).
<p>The SANE API transmits an image as a sequence of frames. Each frame covers
the same rectangular area as the entire image, but may contain only a subset
of the channels in the final image. For example, a red/green/blue image could
either be transmitted as a single frame that contains the sample values for
all three channels or it could be transmitted as a sequence of three frames:
the first frame containing the red channel, the second the green channel, and
the third the blue channel.
<p>When transmitting an image frame by frame, the frontend needs to know what
part of the image a frame represents (and how many frames it should expect).
For that purpose, the SANE API tags every frame with a type and a format
descriptor.
<p><font color="darkgreen">
There are two different types of frames: pixel oriented frames
<tt>SANE_FRAME_RAW<a name="i1"></tt> and arbitrary data frames
<tt>SANE_FRAME_MIME<a name="i2"></tt>. These types are discussed in detail in the
following sections. The frame types used by the previous version 1 of this
standard (<tt>SANE_FRAME_GRAY<a name="i3"></tt>, <tt>SANE_FRAME_RGB<a name="i4"></tt>,
<tt>SANE_FRAME_RED<a name="i5"></tt>, <tt>SANE_FRAME_GREEN<a name="i6"></tt>, and
<tt>SANE_FRAME_BLUE<a name="i7"></tt>) are obsolete and superseded by
<tt>SANE_FRAME_RAW<a name="i8"></tt>.
<p> <h3><a name="s3.2.1">3.2.1 Pixel oriented frames</a></h3>
<p> The type of pixel oriented frames is <tt>SANE_FRAME_RAW<a name="i9"></tt>. The
frame contains one or more channels of data in a channel-interleaved format,
that represents sample values from a property of the individual pixels that
is subject to further description in the <tt>format_desc</tt> member of the
<tt>SANE_Parameters</tt> structured type. See section <a href="doc012.html#s4.3.8">4.3.8</a>
on page <a href="doc012.html#s4.3.8">4.3.8</a> for details about the format
descriptions.
</font>
<p> Each sample value has a certain bit depth. The bit depth is fixed for the
entire image and can be as small as one bit. Valid bit depths are 1, 8, or
16 bits per sample. If a device's natural bit depth is something else, it is
up to the driver to scale the sample values appropriately (e.g., a 4 bit
sample could be scaled by a factor of four to represent a sample value of
depth 8).
<p><font color="darkgreen">
The complete image may consist of several different channels. The number of channels
is defined by member <tt>channels_per_image</tt> of <tt>SANE_Parameters</tt>.
The image may be transmitted in an arbitrary number of frames which can be
determined by watching the <tt>SANE_PFLAG_LAST_FRAME</tt> flag in said type (or by
counting the channels). Note: This frame type replaces all frame types of
the SANE standard version 1.
</font>
<p>Conceptually, each pixel oriented frame is transmitted a byte at a time. Each
byte may contain 8 sample values (for an image bit depth of 1), one full
sample value (for an image bit depth of 8), or a partial sample value (for an
image bit depth of 16 or bigger). In the latter case, the bytes of each
sample value are transmitted in the machine's native byte order.
<blockquote>
<center>
<b>Backend Implementation Note</b>
</center>
A network-based meta backend will have to ensure that the byte order
in image data is adjusted appropriately if necessary. For example,
when the meta backend attaches to the server proxy, the proxy may
inform the backend of the server's byte order. The backend can then
apply the adjustment if necessary. In essence, this implements a
``receiver-makes-right'' approach.
</blockquote>
<p><p><a name="f2"></a>
<center>
<img width=390 height=196 src="img001.gif">
<p><center>Figure 2: Transfer order of image data bytes</center>
</center>
<p>
<p>The order in which the sample values in a frame are transmitted is illustrated
in Figure <a href="doc008.html#f2">2</a>. As can be seen, the values are transmitted row by
row and each row is transmitted from left-most to right-most column. The
left-to-right, top-to-bottom transmission order applies when the image is
viewed in its normal orientation (as it would be displayed on a screen, for
example).
<p>If a frame contains multiple channels, then the channels are transmitted in an
interleaved fashion. Figure <a href="doc008.html#f3">3</a> illustrates this for the case
where a frame contains a complete red/green/blue image with a bit-depth of 8.
<p><p><a name="f3"></a>
<center>
<img width=624 height=111 src="img002.gif">
<p><center>Figure 3: Bit and byte order of image data</center>
</center>
<p>
<p>For a bit depth of 1, each byte contains 8 sample values of a <em>single</em>
channel. In other words, a bit depth 1 frame is transmitted in a byte
interleaved fashion. The first sample of each byte is represented by the most
significant bit.
<p><font color="darkgreen">
For gray channels at a bit depth of 1 only two sample values are possible: 1
represents minimum intensity (black) and 0 represents maximum intensity
(white). For all other channel types and bit depths a sample value of 0
represents minimum intensity and larger values represent increasing intensity.
<p><h3><a name="s3.2.2">3.2.2 Arbitrary data frames</a></h3>
<p>It also is possible to transmit arbitrary (not necessaryly pixel oriented)
data. This allows transmission of compressed images like jpeg, tiff, etc.
<p>The type of arbitrary data frames is <tt>SANE_FRAME_MIME<a name="i10"></tt>.
The frame contains arbitrary data of the MIME (see RFC 1521/1522) type that is
given in the <tt>format_desc</tt> member of the <tt>SANE_Parameters</tt>
structured type (see section <a href="doc012.html#s4.3.8">4.3.8</a> on
page <a href="doc012.html#s4.3.8">4.3.8</a>). As such, it is assumed to be
incomprehensible to the frontend, except for selected types the frontend is
specifically capable of handling internally. The frontend is free to ignore
those frames, or employ any appropriate means to otherwise handle this data
(like saving them to disk or spawning an external viewer).
</font>
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<title>The SANE Application Programmer Interface (API)</title>
<h1><a name="s4">4 The SANE Application Programmer Interface (API)</a></h1>
<p><font color="darkgreen">
This Section defines version 2 of the SANE application
programmer interface (API). Any SANE frontend must depend on the
interface defined in this section only. Converseley, any SANE backend
must implement its functionality in accordance with this
specification. The interface as documented here is declared as a C
callable interface in a file called <tt>sane/sane-2.h</tt>. This file should
normally be included via a C pre-processor directive of the form:
<pre>
#include &lt;sane/sane-2.h&gt;
</pre>
</font>
<p><h2><a href="doc010.html">4.1 Version Control</a></h2><h2><a href="doc011.html">4.2 Data Types</a></h2><h2><a href="doc012.html">4.3 Operations</a></h2><h2><a href="doc013.html">4.4 Code Flow</a></h2><h2><a href="doc014.html">4.5 Well-Known Options</a></h2><p><hr>
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<title>Version Control</title>
<h2><a name="s4.1">4.1 Version Control</a></h2>
<p>The SANE standard is expected to evolve over time. Whenever a change
to the SANE standard is made that may render an existing frontend or
backend incompatible with the new standard, the major version number
must be increased. Thus, any frontend/backend pair is compatible
provided the major version number of the SANE standard they implement
is the same. A frontend may implement backwards compatiblity by
allowing major numbers that are smaller than the expected major number
(provided the frontend really can cope with the older version). In
contrast, a backend always provides support for one and only one
version of the standard. If a specific application does require that
two different versions of the same backend are accessible at the same
time, it is possible to do so by installing the two versions under
different names.
<p>SANE version control also includes a minor version number and a build
revision. While control of these numbers remains with the implementor
of a backend, the recommended use is as follows. The minor version is
incremented with each official release of a backend. The build
revision is increased with each build of a backend.
<p>The SANE API provides the following five macros to manage version
numbers.
<blockquote>
<dl>
<dt><tt>SANE_CURRENT_MAJOR<a name="i11"></tt>:<dd> The value of this macro is the
number of the SANE standard that the interface implements.
<p> <dt><tt>SANE_VERSION_CODE<a name="i12">(<i>maj</i>,<i>min</i>,<i>bld</i>)</tt>:<dd>
This macro can be used to build a monotonically increasing version
code. A SANE version code consists of the SANE standard major
version number (<i>maj</i>), the minor version number <i>min</i>,
and the build revision of a backend (<i>bld</i>). The major and
minor version numbers must be in the range 0...255 and the
build revision must be in the range 0...65535.
<p> Version codes are monotonic in the sense that it is possible to
apply relational operators (e.g., equality or less-than test)
directly on the version code rather than individually on the three
components of the version code.
<p> Note that the major version number alone determines whether a
frontend/backend pair is compatible. The minor version and the
build revision are used for informational and bug-fixing purposes
only.
<dt><tt>SANE_VERSION_MAJOR<a name="i13">(<i>vc</i>)</tt>:<dd> This macro returns the
major version number component of the version code passed in
argument <i>vc</i>.
<dt><tt>SANE_VERSION_MINOR(<i>vc</i>)</tt>:<dd> This macro returns the
minor version number component of the version code passed in
argument <i>vc</i>.
<dt><tt>SANE_VERSION_BUILD(<i>vc</i>)</tt>:<dd> This macro returns the
build revision component of the version code passed in argument
<i>vc</i>.
</dl>
</blockquote>
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<title>Operations</title>
<h2><a name="s4.3">4.3 Operations</a></h2>
<p><h3><a name="s4.3.1">4.3.1 <tt>sane_init</tt></a></h3>
<p>This function must be called before any other SANE function can be called.
The behavior of a SANE backend is undefined if this function is not called
first or if the status code returned by <tt>sane_init</tt> is different from
<tt>SANE_STATUS_GOOD<a name="i79"></tt>. The version code of the backend is returned
in the value pointed to by <tt>version_code</tt>. If that pointer is
<tt>NULL</tt>, no version code is returned. Argument <tt>authorize</tt> is either
a pointer to a function that is invoked when the backend requires
authentication for a specific resource or <tt>NULL</tt> if the frontend does not
support authentication.
<blockquote><a name="i80">
<pre>
SANE_Status sane_init (SANE_Int * version_code,
SANE_Authorization_Callback authorize);
</pre>
</blockquote>
<p>The authorization function may be called by a backend in response to
any of the following calls:
<blockquote>
<tt>sane_open</tt>, <tt>sane_control_option</tt>, <tt>sane_start</tt>
</blockquote>
If a backend was initialized without authorization function, then
authorization requests that cannot be handled by the backend itself
will fail automatically and the user may be prevented from accessing
protected resources. Backends are encouraged to implement means of
authentication that do not require user assistance. E.g., on a
multi-user system that authenticates users through a login process a
backend could automatically lookup the apporpriate password based on
resource- and user-name.
<p>The authentication function type has the following declaration:
<blockquote><a name="i81">
<a name="i82"><a name="i83"><a name="i84">
<pre>
#define SANE_MAX_USERNAME_LEN 128
#define SANE_MAX_PASSWORD_LEN 128
typedef void (*SANE_Authorization_Callback)
(SANE_String_Const resource,
SANE_Char username[SANE_MAX_USERNAME_LEN],
SANE_Char password[SANE_MAX_PASSWORD_LEN]);
</pre>
</blockquote>
Three arguments are passed to the authorization function:
<tt>resource</tt> is a string specifying the name of the resource that
requires authorization. A frontend should use this string to build a
user-prompt requesting a username and a password. The <tt>username</tt>
and <tt>password</tt> arguments are (pointers to) an array of
<tt>SANE_MAX_USERNAME_LEN</tt> and <tt>SANE_MAX_PASSWORD_LEN</tt>
characters, respectively. The authorization call should place the
entered username and password in these arrays. The returned strings
<em>must</em> be ASCII-NUL terminated.
<p><h3><a name="s4.3.2">4.3.2 <tt>sane_exit</tt></a></h3>
<p>This function must be called to terminate use of a backend. The
function will first close all device handles that still might be open
(it is recommended to close device handles explicitly through a call
to <tt>sane_close()</tt>, but backends are required to release all
resources upon a call to this function). After this function returns,
no function other than <tt>sane_init()</tt> may be called (regardless
of the status value returned by <tt>sane_exit()</tt>. Neglecting to
call this function may result in some resources not being released
properly.
<blockquote><a name="i85">
<pre>
void sane_exit (void);
</pre>
</blockquote>
<p><h3><a name="s4.3.3">4.3.3 <tt>sane_get_devices</tt></a></h3>
<p>This function can be used to query the list of devices that are
available. If the function executes successfully, it stores a pointer
to a <tt>NULL</tt> terminated array of pointers to <tt>SANE_Device</tt>
structures in <tt>*device_list</tt>. The returned list is guaranteed
to remain unchanged and valid until (a) another call to this function
is performed or (b) a call to <tt>sane_exit()</tt> is performed. This
function can be called repeatedly to detect when new devices become
available. If argument <tt>local_only</tt> is true, only local devices
are returned (devices directly attached to the machine that SANE is
running on). If it is false, the device list includes all remote
devices that are accessible to the SANE library.
<blockquote><a name="i86">
<pre>
SANE_Status sane_get_devices (const SANE_Device *** device_list,
SANE_Bool local_only);
</pre>
</blockquote>
<p>This function may fail with <tt>SANE_STATUS_NO_MEM</tt> if an
insufficient amount of memory is available.
<p><blockquote>
<center>
<b>Backend Implementation Note</b>
</center>
SANE does not require that this function is called before a
<tt>sane_open()</tt> call is performed. A device name may be
specified explicitly by a user which would make it unnecessary and
undesirable to call this function first.
<font color="darkgreen">
The same information about
a device has to be returned when <tt>sane_open</tt> is called.
</font>
</blockquote>
<p><h3><a name="s4.3.4">4.3.4 <tt>sane_open</tt></a></h3>
<p>This function is used to establish a connection to a particular
device. The name of the device to be opened is passed in argument
<tt>name</tt>. If the call completes successfully, a handle for the
device is returned in <tt>*h</tt>.
<font color="darkgreen">
The description of the device
is returned in <tt>**device_description</tt>. This is the
same description that is returned in the list by <tt>sane_get_devices</tt>.
The returned data <tt>*h</tt> and <tt>*device_description</tt> is guaranteed
to remain unchanged and valid until a call to <tt>sane_close()</tt>
is performed.
</font>
As a special case, specifying a zero-length string as the device requests
opening the first available device (if there is such a device).
<blockquote><a name="i87">
<pre>
SANE_Status sane_open (SANE_String_Const name, SANE_Handle * h,
const SANE_Device ** device_description);
</pre>
</blockquote>
<p>This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_DEVICE_BUSY</tt>:<dd> The device is currently
busy (in use by somebody else).
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> The device name is not valid.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occured while
communicating with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_ACCESS_DENIED</tt>:<dd> Access to the device has
been denied due to insufficient or invalid authentication.
</dl>
</blockquote>
<p><h3><a name="s4.3.5">4.3.5 <tt>sane_close</tt></a></h3>
<p>This function terminates the association between the device handle
passed in argument <tt>h</tt> and the device it represents. If the
device is presently active, a call to <tt>sane_cancel()</tt> is
performed first. After this function returns, handle <tt>h</tt> must
not be used anymore.
<p><blockquote><a name="i88">
<pre>
void sane_close (SANE_Handle h);
</pre>
</blockquote>
<p><h3><a name="s4.3.6">4.3.6 <tt>sane_get_option_descriptor</tt></a></h3>
<p>This function is used to access option descriptors. The function
returns the option descriptor for option number <tt>n</tt> of the device
represented by handle <tt>h</tt>. Option number 0 is guaranteed to be a
valid option. Its value is an integer that specifies the number of
options that are available for device handle <tt>h</tt> (the count
includes option 0). If n is not a valid option index, the function
returns <tt>NULL</tt>. The returned option descriptor is guaranteed to
remain valid (and at the returned address) until the device is closed.
<p><blockquote><a name="i89">
<pre>
const SANE_Option_Descriptor *
sane_get_option_descriptor (SANE_Handle h, SANE_Int n);
</pre>
</blockquote>
<p><h3><a name="s4.3.7">4.3.7 <tt>sane_control_option</tt></a></h3>
<p>This function is used to set or inquire the current value of option
number <tt>n</tt> of the device represented by handle <tt>h</tt>. The
manner in which the option is controlled is specified by parameter
<tt>a</tt>. The possible values of this parameter are described in more
detail below. The value of the option is passed through argument
<tt>v</tt>. It is a pointer to the memory that holds the option value.
The memory area pointed to by <tt>v</tt> must be big enough to hold the
entire option value (determined by member <tt>size</tt> in the
corresponding option descriptor). The only exception to this rule is
that when setting the value of a string option, the string pointed to
by argument <tt>v</tt> may be shorter since the backend will stop
reading the option value upon encountering the first <tt>NUL</tt>
terminator in the string. If argument <tt>i</tt> is not <tt>NULL</tt>,
the value of <tt>*i</tt> will be set to provide details on how well the
request has been met. The meaning of this argument is described in
more detail below.
<blockquote><a name="i90">
<pre>
SANE_Status sane_control_option (SANE_Handle h, SANE_Int n,
SANE_Action a, void *v,
SANE_Int * i);
</pre>
</blockquote>
<p>The way the option is affected by a call to this function is
controlled by parameter <tt>a</tt> which is a value of type
<tt>SANE_Action<a name="i91"></tt>. The possible values and their meaning is
described in Table <a href="doc012.html#t7">7</a>.
<p><p><a name="t7"></a>
<center>
<table cellpadding=0 cellspacing=0 border=1>
<tr valign=top>
<td colspan=1 align=center nowrap><b>Symbol</b></td>
<td colspan=1 align=center nowrap><b>Code</b></td>
<td colspan=1 align=center nowrap><b>Description</b></td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
<p><tt>SANE_ACTION_GET_VALUE<a name="i92"></tt> </td>
<td colspan=1 align=right nowrap> 0 </td>
<td colspan=1 align=left> Get current option value. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_ACTION_SET_VALUE<a name="i93"></tt> </td>
<td colspan=1 align=right nowrap> 1 </td>
<td colspan=1 align=left> Set option value. The
option value passed through argument <tt>v</tt> may be modified by the
backend if the value cannot be set exactly. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_ACTION_SET_AUTO<a name="i94"></tt> </td>
<td colspan=1 align=right nowrap> 2 </td>
<td colspan=1 align=left> Turn on automatic mode. Backend
or device will automatically select an appropriate value. This mode
remains effective until overridden by an explicit set value request.
The value of parameter <tt>v</tt> is completely ignored in this case and
may be <tt>NULL</tt>. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
</td></tr>
</table>
<p><center>Table 7: Action Values (<tt>SANE_Action</tt>)</center>
</center>
<p>
<p>After setting a value via an action value of
<tt>SANE_ACTION_SET_VALUE</tt>, additional information on how well the
request has been met is returned in <tt>*i</tt> (if <tt>i</tt> is
non-<tt>NULL</tt>). The returned value is a bitset that may contain any
combination of the values described in Table <a href="doc012.html#t8">8</a>.
<p><a name="t8"></a>
<center>
<table cellpadding=0 cellspacing=0 border=1>
<tr valign=top>
<td colspan=1 align=center nowrap><b>Symbol</b></td>
<td colspan=1 align=center nowrap><b>Code</b></td>
<td colspan=1 align=center nowrap><b>Description</b></td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
<p><tt>SANE_INFO_INEXACT<a name="i95"></tt> </td>
<td colspan=1 align=right nowrap> 1 </td>
<td colspan=1 align=left> This value is returned when
setting an option value resulted in a value being selected that does
not exactly match the requested value. For example, if a scanner
can adjust the resolution in increments of 30dpi only, setting the
resolution to 307dpi may result in an actual setting of 300dpi.
When this happens, the bitset returned in <tt>*i</tt> has this member
set. In addition, the option value is modified to reflect the
actual (rounded) value that was used by the backend. Note that
inexact values are admissible for strings as well. A backend may
choose to ``round'' a string to the closest matching legal string
for a constrained string value. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_INFO_RELOAD_OPTIONS<a name="i96"></tt> </td>
<td colspan=1 align=right nowrap> 2 </td>
<td colspan=1 align=left>
The setting of an option may affect the
<font color="darkgreen">
value, the availability, or the constraint of one or more <em>
other</em> options.
</font>
When this happens, the SANE backend sets this
member in <tt>*i</tt> to indicate that the application should reload
all options. This member may be set if and only if at least one
option changed. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_INFO_RELOAD_PARAMS<a name="i97"></tt> </td>
<td colspan=1 align=right nowrap> 4 </td>
<td colspan=1 align=left>
The setting of an option may affect the parameter values (see
<tt>sane_get_parameters()</tt>).
If setting an option affects the parameter values, this member will
be set in <tt>*i</tt>. Note that this member may be set even if the
parameters did not actually change. However, it is guaranteed that
the parameters never change without this member being set.
</td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p><tt>SANE_INFO_INVALIDATE_PREVIEW<a name="i98"></tt> </td>
<td colspan=1 align=right nowrap> 8 </td>
<td colspan=1 align=left>
The setting of an option may affect the validity of the preview that
was acquired by the frontend earlier. When the preview image would change
significantly if it was scanned again, the SANE backend
sets this member in <tt>*i</tt> to indicate that the application should inform the
user of the invalidity of the preview. Examples for such option
settings may include setting a different scan source or significantly
changing the exposure.
</td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
</td></tr>
</table>
<p><center>Table 8: Additional Information Returned When Setting an Option</center>
</center>
<p>
<p>This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_UNSUPPORTED</tt>:<dd> The operation is not
supported for the specified handle and option number.
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> The option value is not valid.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occured while
communicating with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_ACCESS_DENIED</tt>:<dd> Access to the option has
been denied due to insufficient or invalid authentication.
</dl>
</blockquote>
<p><h3><a name="s4.3.8">4.3.8 <tt>sane_get_parameters</tt></a></h3>
<p>This function is used to obtain the current scan parameters. The
returned parameters are guaranteed to be accurate between the time a
scan has been started (<tt>sane_start()</tt> has been called) and the
completion of that request. Outside of that window, the returned
values are best-effort estimates of what the parameters will be when
<tt>sane_start()</tt> gets invoked. Calling this function before a
scan has actually started allows, for example, to get an estimate of
how big the scanned image will be. The parameters passed to this
function are the handle <tt>h</tt> of the device for which the
parameters should be obtained and a pointer <tt>p</tt> to a parameter
structure. The parameter structure is described in more detail below.
<p><blockquote><a name="i99">
<pre>
SANE_Status sane_get_parameters (SANE_Handle h,
SANE_Parameters * p);
</pre>
</blockquote>
<p>The scan parameters are returned in a structure of type
<tt>SANE_Parameters<a name="i100"></tt>. The C declaration of this structure
is given below.
<font color="darkgreen">
<blockquote>
<pre>
typedef struct
{
SANE_Frame format;
SANE_Int flags;
SANE_Int lines;
SANE_Int depth;
SANE_Int pixels_per_line;
SANE_Int bytes_per_line;
SANE_Int channels_per_image;
SANE_String format_desc;
SANE_String proposed_filename;
SANE_String proposed_comment;
SANE_Int dpi_x;
SANE_Int dpi_y;
char reserved[32]; /* 32 bytes for future use */
}
SANE_Parameters;
</pre>
</blockquote>
</font>
<p><font color="darkgreen">
Member <tt>format</tt> specifies the format of the next frame to be
returned. The possible values for type <tt>SANE_Frame<a name="i101"></tt> are
described in Table <a href="doc012.html#t9">9</a>. The meaning of these
values is described in more detail in section <a href="doc008.html#s3.2">3.2</a>.
The frame types used by version 1 of this standard
(<tt>SANE_FRAME_GRAY<a name="i102"></tt>, <tt>SANE_FRAME_RGB<a name="i103"></tt>,
<tt>SANE_FRAME_RED<a name="i104"></tt>, <tt>SANE_FRAME_GREEN<a name="i105"></tt>, and
<tt>SANE_FRAME_BLUE<a name="i106"></tt>) are obsolete and superseded by the
frame type <tt>SANE_FRAME_RAW<a name="i107"></tt>.
<p><p><a name="t9"></a>
<center>
<table cellpadding=0 cellspacing=0 border=1>
<tr valign=top>
<td colspan=1 align=center nowrap><b>Symbol</b></td>
<td colspan=1 align=center nowrap><b>Code</b></td>
<td colspan=1 align=center nowrap><b>Description</b></td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
<p><tt>SANE_FRAME_RAW<a name="i108"></tt> </td>
<td colspan=1 align=right nowrap> 5 </td>
<td colspan=1 align=left nowrap> Arbitrary pixel property transmission. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_FRAME_MIME<a name="i109"></tt> </td>
<td colspan=1 align=right nowrap> 6 </td>
<td colspan=1 align=left nowrap> Data described by a mime descriptor. </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<p>
</td></tr>
</table>
<p><center>Table 9: Frame Format (<tt>SANE_Frame</tt>)</center>
</center>
<p>
<p>The <tt>flags</tt> member is a 32 bit bitfield, for which up to now 4
informational bits are defined, all unused bits have to be set to 0:
<p><ul>
<p><li>
<tt>SANE_PFLAG_LAST_FRAME</tt> (bit 0, bitvalue 1) is set to 1 if and
only if the frame that is currently being acquired (or the frame that
will be acquired next if there is no current frame) is the only frame
or the last frame
of a multi frame image (e.g., the current frame is the blue component
of a red, green, blue image).
<p><li>
<tt>SANE_PFLAG_MORE_IMAGES</tt> (bit 1, bitvalue 2) is set to 1 to indicate
further pending images. The frontend is expected to call <tt>sane_start</tt>
again after the end of the current scan to get more images, e.g.
from an automatic document feeder. It is permissible to set that value to 1 ``in good
faith'', as it has to be determined at a very early time, where it might
not be detectable, if there actually are more images to transfer. E.g.
you will usually not know if the document feeder contains further pages
when starting to scan the current one. Thus you are allowed to set that
bit but later fail at <tt>sane_start()</tt>.
<p><li>
<tt>SANE_PFLAG_NEW_PAGE</tt> (bit 2, bitvalue 4) is set to 1 to indicate
that the current frame comes from a new physical page. This bit is of
informational character only to help frontends to group multi-image
scans.
<p><li>
<tt>SANE_PFLAG_BACKSIDE</tt> (bit 3, bitvalue 8) tells if the current image
was acquired from the front (0) or backside (1) of the currently processed
sheet. It is of informational character and allows to group and order
multi-image transfers regardless of scanner acquisition order (front
first/back first).
<p></ul>
<p>Note, that <tt>flags</tt> is compatible to member <tt>last_frame</tt> of
<tt>SANE_Parameters</tt> of SANE standard version 1 (same size
and only bit 0 (bitvalue 1) was used with same function).
</font>
<p>Member <tt>lines</tt> specifies how many scan lines the frame is
comprised of. If this value is -1, the number of lines is not known a
priori and the frontend should call <tt>sane_read()</tt> until it
returns a status of <tt>SANE_STATUS_EOF</tt>.
<font color="darkgreen">
Note, that even when transferring formats that have this information
inband, it is recommended to set that member, if available. If
unavailable or not applicable, set to -1 as mentioned above.
</font>
<p>Member <tt>bytes_per_line</tt> specifies the number of bytes that comprise one
scan line.
<font color="darkgreen">
If this value is not applicable for image data of type
<tt>SANE_FRAME_MIME</tt>, it must be set to -1. In this case the frontend
should just call <tt>sane_read</tt> until <tt>SANE_STATUS_EOF</tt> is returned.
</font>
<p>Member <tt>depth</tt> specifies the number of bits per sample.
<font color="darkgreen">
Note, that only -1 (for not applicable), 1, and multiples of 8 are
allowed values. Data with other depths has to be scaled up accordingly.
Depth 1 is only allowed if the image consists of a single channel (lineart or
halftone modes).
</font>
<p>Member <tt>pixels_per_line</tt> specifies the number of pixels that
comprise one scan line.
<font color="darkgreen">
If unavailable or not applicable, set to -1.
</font>
<p>Assume B is the number of channels in the frame, then the bit depth
d (as given by member <tt>depth</tt>) and the number of pixels per
line n (as given by this member <tt>pixels_per_line</tt>) are
related to c, the number of bytes per line (as given by member
<tt>bytes_per_line</tt>) as follows:
<font color="darkgreen">
<p>
<center>
c &gt;= \left{
ll
\lceil B*n / 8\rceil if d=1
</td><td align=right>(1)</td></tr><tr><td align=center>
B*n *d / 8 if d&gt;1
\right.
</center>
<p>
</font>
Note that the number of bytes per line can be larger than the minimum
value imposed by the right side of this equation. A frontend must be
able to properly cope with such ``padded'' image formats.
<p><font color="darkgreen">
Member <tt>channels_per_image</tt> specifies the number of channels the
image consists of. When the image is transmitted in more than one frame
<tt>channels_per_image</tt> has to be the same for all frames for this image.
<p>Member <tt>format_desc</tt> is used to describe the details of the frame
formats. Its meaning differs between the two formats:
<p><ul>
<li>
<tt>SANE_FRAME_RAW</tt>:
The <tt>format_desc</tt> contains a description of the channel data and
an optional depth information separated by a colon(:).
<p>A plane is descibed by one channel, e.g. ``<tt>gray</tt>'' or ``<tt>gray:12</tt>''.
<p>Channel interleaved data is described by a comma separated list of channel descriptions,
for example ``<tt>red,green,blue</tt>'' or ``<tt>red:8,green:8,blue:8</tt>'',
the channel data is sent in the given order.
<p>The depth information does <b>not</b> define the size of the transmitted
channel data, it is only an information for the frontend. The channel data has
to be sent in the size defined by member <tt>depth</tt>.
<p>Well known channels are <tt>red</tt>, <tt>green</tt>, <tt>blue</tt> and <tt>gray</tt>.
It also is allowed to use other channel descriptions, e.g. if you
use an infrared camera or scanner it could be <tt>infrared</tt> or
a wavelength description like <tt>1100nm</tt>, but be aware that a
frontend may not be able to display such channels with useful colors.
<p>Note that an image can be sent in single planes, in one interleaved
frame that contains all channels or in several frames that contain
one or more (interleaved) channels. When an RGB image is sent it
is prefered to send the image data in one interleaved frame
that consist of red, green and blue data in this order.
The number of channels is defined in member <tt>channels_per_image</tt>.
<p><li>
<tt>SANE_FRAME_MIME</tt>:
<p><tt>format_desc</tt> contains the MIME Content-Type: header field as described
in RFC 1521 (section 4) without the prefixing "Content-Type:". MIME Types and
subtypes should be either chosen from the RFC or from the list of
IANA-approved values. The data stream must be compliant with the corresponding
specification.
<p>When data is transmitted with the frame type <tt>SANE_FRAME_MIME</tt>
all data has to be transmitted within one frame, multiple frames
are not allowed (so the flag <tt>last_frame</tt> has to be set
when using this frame type).
<p>A SANE backend must be able to at least optionally transmit
<tt>SANE_FRAME_RAW</tt> (possibly with the help of a meta backend), if the
hardware supports delivering image data at all. For data that doesn't
comprise images, it's admisable to only provide MIME frames. As a
general principle, if there are several choices in MIME types, the
format that is most widely implemented should be used.
</ul>
<p>The member <tt>proposed_filename</tt> can be used to suggest a reasonable
default filename or -extension in case the backend can make such a
suggestion, like e.g. an image database.
If no such suggestion is intended, set the field to ``''.
<p>In the case of raw frames, <tt>proposed_filename</tt> is expected to hold
the basename for the image, with the extension determined by the save function
of the frontend, as the frontend can fully understand the data and is thus
able to encode it in any format it wishes.
<p>For MIME frames <tt>proposed_filename</tt> can contain either:
<p><ul>
<li>
A name with a leading dot, which is considered to be a proposed
filename extension. This could also be gotten from the mime database,
but for systems lacking it, this might be convenient. Or:
<p><li>
A complete filename, including extension.
</ul>
<p>Note, that for frontends that are able to parse a given MIME type
internally, it is perfectly permissible to ignore the extension
part of the proposed filename and only make use of the basename,
when using internal save algorithms for different formats.
<p>The string <tt>proposed_comment</tt> can be used to transmit additional
image information, that can be stored in the comment areas several file formats
offer. It can contain any textual information the backend wishes to
convey to the user, like date/time of exposure, enganged filters,
etc. Set to ``'' if unused.
<p>The members <tt>dpi_x</tt> and <tt>dpi_y</tt> encode the horizontal and vertical
resolution. Note, that multiple-image scans may have different resolutions of
each image. It is not permissible to change resolution between frames of the
same image. If not applicable, set to -1.
<p>The member <tt>reserved</tt> is an array of 32 bytes (char) to keep
the size of the struct unchanged when future extensions are done.
The backend has to set the reserved bytes to 0.
</font>
<p><h3><a name="s4.3.9">4.3.9 <tt>sane_start</tt></a></h3>
<p>This function initiates aquisition of an image from the device
represented by handle <tt>h</tt>.
<blockquote><a name="i110">
<pre>
SANE_Status sane_start (SANE_Handle h);
</pre>
</blockquote>
This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_CANCELLED</tt>:<dd> The operation was cancelled through
a call to <tt>sane_cancel</tt>.
<dt><tt>SANE_STATUS_DEVICE_BUSY</tt>:<dd> The device is busy. The
operation should be retried later.
<dt><tt>SANE_STATUS_JAMMED</tt>:<dd> The document feeder is jammed.
<dt><tt>SANE_STATUS_NO_DOCS</tt>:<dd> The document feeder is out of
documents.
<dt><tt>SANE_STATUS_COVER_OPEN</tt>:<dd> The scanner cover is open.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occurred while communicating
with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> The scan cannot be started with the current
set of options. The frontend should reload the option descriptors, as if
<tt>SANE_INFO_RELOAD_OPTIONS<a name="i111"></tt> had been returned from a call to
<tt>sane_control_option()</tt>, since the device's capabilities may have
changed.
</dl>
</blockquote>
<p><h3><a name="s4.3.10">4.3.10 <tt>sane_read</tt></a></h3>
<p>This function is used to read image data from the device represented
by handle <tt>h</tt>. Argument <tt>buf</tt> is a pointer to a memory area
that is at least <tt>maxlen</tt> bytes long. The number of bytes
returned is stored in <tt>*len</tt>. A backend must set this to zero
when a status other than <tt>SANE_STATUS_GOOD</tt> is returned).
When the call succeeds, the number of bytes returned can be anywhere in
the range from 0 to <tt>maxlen</tt> bytes.
<blockquote><a name="i112">
<pre>
SANE_Status sane_read (SANE_Handle h, SANE_Byte * buf,
SANE_Int maxlen, SANE_Int * len);
</pre>
</blockquote>
<font color="darkgreen">
For efficiency reasons, medium to large
block sizes (in the range of a few kilobytes) should be used.
Returning short reads is allowed to allow for small buffers
in the backend.
</font>
If this function is called when no data is available, one of two
things may happen, depending on the I/O mode that is in effect for
handle <tt>h</tt>.
<ol>
<li>If the device is in blocking I/O mode (the default mode), the
call blocks until at least one data byte is available (or until some
error occurs).
<p><li>If the device is in non-blocking I/O mode, the call returns
immediately with status <tt>SANE_STATUS_GOOD</tt> and with
<tt>*len</tt> set to zero.
</ol>
The I/O mode of handle <tt>h</tt> can be set via a call to
<tt>sane_set_io_mode()</tt>.
<p>This function may fail with one of the following status codes.
<blockquote>
<dl>
<dt><tt>SANE_STATUS_CANCELLED</tt>:<dd> The operation was cancelled through
a call to <tt>sane_cancel</tt>.
<dt><tt>SANE_STATUS_EOF</tt>:<dd> No more data is available for the
current frame.
<font color="darkgreen">
If <tt>sane_read</tt> sends back any image data it
is not allowed to return with <tt>SANE_STATUS_EOF</tt>.
</font>
<dt><tt>SANE_STATUS_JAMMED</tt>:<dd> The document feeder is jammed.
<dt><tt>SANE_STATUS_NO_DOCS</tt>:<dd> The document feeder is out of
documents.
<dt><tt>SANE_STATUS_COVER_OPEN</tt>:<dd> The scanner cover is open.
<dt><tt>SANE_STATUS_IO_ERROR</tt>:<dd> An error occurred while communicating
with the device.
<dt><tt>SANE_STATUS_NO_MEM</tt>:<dd> An insufficent amount of memory
is available.
<dt><tt>SANE_STATUS_ACCESS_DENIED</tt>:<dd> Access to the device has
been denied due to insufficient or invalid authentication.
</dl>
</blockquote>
<p><h3><a name="s4.3.11">4.3.11 <tt>sane_cancel</tt></a></h3>
<p>This function is used to immediately or as quickly as possible cancel
the currently pending operation of the device represented by handle
<tt>h</tt>.
<blockquote><a name="i113">
<pre>
void sane_cancel (SANE_Handle h);
</pre>
</blockquote>
This function can be called at any time (as long as handle <tt>h</tt> is
a valid handle) but usually affects long-running operations only (such
as image is acquisition). It is safe to call this function
asynchronously (e.g., from within a signal handler). It is important
to note that completion of this operaton does <em>not</em> imply that
the currently pending operation has been cancelled. It only
guarantees that cancellation has been <em>initiated</em>. Cancellation
completes only when the cancelled call returns (typically with a
status value of <tt>SANE_STATUS_CANCELLED</tt>). Since the SANE API
does not require any other operations to be re-entrant, this implies
that a frontend must <em>not</em> call any other operation until the
cancelled operation has returned.
<p><h3><a name="s4.3.12">4.3.12 <tt>sane_set_io_mode</tt></a></h3>
<p>This function is used to set the I/O mode of handle <tt>h</tt>. The I/O mode
can be either blocking or non-blocking. If argument <tt>m</tt> is
<tt>SANE_TRUE</tt>, the mode is set to non-blocking mode, otherwise it's set to
blocking mode. This function can be called only after a call to
<tt>sane_start()</tt> has been performed.
<blockquote><a name="i114">
<pre>
SANE_Status sane_set_io_mode (SANE_Handle h, SANE_Bool m);
</pre>
</blockquote>
By default, newly opened handles operate in blocking mode. A backend
may elect not to support non-blocking I/O mode. In such a case the
status value <tt>SANE_STATUS_UNSUPPORTED</tt> is returned. Blocking
I/O must be supported by all backends, so calling this function with
argument <tt>m</tt> set to <tt>SANE_FALSE</tt> is guaranteed to complete
successfully.
<p>This function may fail with one of the following status codes:
<blockquote>
<dl>
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> No image acquisition is pending.
<dt><tt>SANE_STATUS_UNSUPPORTED</tt>:<dd> The backend does not support
the requested I/O mode.
</dl>
</blockquote>
<p><h3><a name="s4.3.13">4.3.13 <tt>sane_get_select_fd</tt></a></h3>
<p>This function is used to obtain a (platform-specific) file-descriptor
for handle <tt>h</tt> that is readable if and only if image data is
available (i.e., when a call to <tt>sane_read()</tt> will return at
least one byte of data). If the call completes successfully, the
select file-descriptor is returned in <tt>*fd</tt>.
<blockquote><a name="i115">
<pre>
SANE_Status sane_get_select_fd (SANE_Handle h, SANE_Int *fd);
</pre>
</blockquote>
This function can be called only after a call to <tt>sane_start()</tt>
has been performed and the returned file-descriptor is guaranteed to
remain valid for the duration of the current image acquisition (i.e.,
until <tt>sane_cancel()</tt> or <tt>sane_start()</tt> get called again
or until <tt>sane_read()</tt> returns with status
<tt>SANE_STATUS_EOF</tt>). Indeed, a backend must guarantee to
close the returned select file descriptor at the point when the next
<tt>sane_read()</tt> call would return <tt>SANE_STATUS_EOF</tt>.
This is necessary to ensure the application can detect when this
condition occurs without actually having to call <tt>sane_read()</tt>.
<p>A backend may elect not to support this operation. In such a case,
the function returns with status code
<tt>SANE_STATUS_UNSUPPORTED</tt>.
<p>Note that the only operation supported by the returned file-descriptor
is a host operating-system dependent test whether the file-descriptor
is readable (e.g., this test can be implemented using <tt>select()</tt>
or <tt>poll()</tt> under UNIX). If any other operation is performed on
the file descriptor, the behavior of the backend becomes
unpredictable. Once the file-descriptor signals ``readable'' status,
it will remain in that state until a call to <tt>sane_read()</tt> is
performed. Since many input devices are very slow, support for this
operation is strongly encouraged as it permits an application to do
other work while image acquisition is in progress.
<p>This function may fail with one of the following status codes:
<blockquote>
<dl>
<dt><tt>SANE_STATUS_INVAL</tt>:<dd> No image acquisition is pending.
<dt><tt>SANE_STATUS_UNSUPPORTED</tt>:<dd> The backend does not support
this operation.
</dl>
</blockquote>
<p><h3><a name="s4.3.14">4.3.14 <tt>sane_strstatus</tt></a></h3>
<p>This function can be used to translate a SANE status code into a
printable string. The returned string is a single line of text that
forms a complete sentence, but without the trailing period
(full-stop). The function is guaranteed to never return <tt>NULL</tt>.
The returned pointer is valid at least until the next call to this
function is performed.
<blockquote><a name="i116">
<pre>
SANE_String_Const sane_strstatus (SANE_Status status);
</pre>
</blockquote>
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<hr>
<title>Code Flow</title>
<h2><a name="s4.4">4.4 Code Flow</a></h2><a name="i117">
<p>The code flow for the SANE API is illustrated in
Figure <a href="doc013.html#f4">4</a>. Functions <tt>sane_init()</tt> and
<tt>sane_exit()</tt> initialize and exit the backend, respectively.
All other calls must be performed after initialization and before
exiting the backend.
<p><p><a name="f4"></a>
<center>
<img width=566 height=510 src="img003.gif">
<p><center>Figure 4: Code flow</center>
</center>
<p>
<p>Function <tt>sane_get_devices()</tt> can be called any time after
<tt>sane_init()</tt> has been called. It returns the list of the
devices that are known at the time of the call. This list may change
over time since some devices may be turned on or off or a remote host
may boot or shutdown between different calls. It should be noted that
this operation may be relatively slow since it requires contacting all
configured devices (some of which may be on remote hosts). A frontend
may therefore want to provide the ability for a user to directly
select a desired device without requiring a call to this function.
<p>Once a device has been chosen, it is opened using a call to
<tt>sane_open()</tt>. Multiple devices can be open at any given time.
A SANE backend must not impose artificial constraints on how many
devices can be open at any given time.
<p>An opened device can be setup through the corresponding device handle
using functions <tt>sane_get_option_descriptor()</tt> and
<tt>sane_control_option()</tt>. While setting up a device, obtaining
option descriptors and setting and reading of option values can be
mixed freely. It is typical for a frontend to read out all available
options at the beginning and then build a dialog (either graphical or
a command-line oriented option list) that allows to control the
available options. It should be noted that the number of options is
fixed for a given handle.
<font color="darkgreen">
However, as options are set, other options may become active or inactive or
their constraint may change. Thus, after setting an option, it may be
necessary to re-read the descriptors.
</font>
While
setting up the device, it is also admissible to call
<tt>sane_get_parameters()</tt> to get an estimate of what the image
parameters will look like once image acquisition begins.
<p>The device handle can be put in blocking or non-blocking mode by a
call to <tt>sane_set_io_mode()</tt>. Devices are required to support
blocking mode (which is the default mode), but support for
non-blocking I/O is strongly encouraged for operating systems such as
UNIX.
<p>After the device is setup properly, image acquisition can be started
by a call to <tt>sane_start()</tt>. The backend calculates the exact
image parameters at this point. So future calls to
<tt>sane_get_parameters()</tt> will return the exact values, rather
than estimates. Whether the physical image acquisition starts at this
point or during the first call to <tt>sane_read()</tt> is unspecified
by the SANE API. If non-blocking I/O and/or a select-style interface
is desired, the frontend may attempt to call
<tt>sane_set_io_mode()</tt> and/or <tt>sane_get_select_fd()</tt> at
this point. Either of these functions may fail if the backend does
not support the requested operation.
<p><font color="darkgreen">
Image data is collected by repeatedly calling <tt>sane_read()</tt>
until this function will return an end-of-file status
(<tt>SANE_STATUS_EOF</tt>). This indicates the end of the current
frame. If the frontend expects additional frames (e.g., the
individual channels of a red/green/blue image or multiple images),
it can call <tt>sane_start()</tt> again.
If the <tt>SANE_PFLAG_LAST_FRAME</tt> bit is set in <tt>flags</tt>, the
current image is complete. In this case, it should be tested, if
<tt>flags</tt> has the <tt>SANE_PFLAG_MORE_IMAGES</tt> bit set.
If yes, further calls to <tt>sane_start()</tt> can be made to acquire
more images. Please note, that as this bit has to be set at the beginning
of a the transmission of the last frame before the new image, it is possible,
that no reliable decision can be made at this time. It is thus permissible
for a backend to set this bit, and then later at the actual call to
<tt>sane_start()</tt> return an error like <tt>SANE_STATUS_NO_DOCS</tt>.
Such a sequence is permitted to transmit multiple images from a single
page as well as multiple pages. This behaviour should be controlled by
backend options as required, to allow single-page scanning as well as
ADF-batch-scanning. The frontend should always continue reading all images
until a frame with <tt>SANE_PFLAG_LAST_FRAME</tt> on
and <tt>SANE_PFLAG_MORE_IMAGES</tt> off is encountered, or an error other
than <tt>SANE_STATUS_EOF</tt> occurs in a SANE function.
Note that <tt>SANE_STATUS_NO_DOCS</tt> also is an allowed way for the backend
to indicate the end of a multiple image scan.
<p>A frontend may choose to skip frames (e.g. because it cannot parse them),
which is accomplished by simply calling <tt>sane_start</tt> again, which will get
you to the next frame, without having to read and discard the current one.
<p>In order to prematurely stop scanning and to reset the backend state,
<tt>sane_cancel()</tt> can be called at any time. This call is required
as well after normal termination of a multiple image scan as described above.
</font>
<p>When done using the device, the handle should be closed by a call to
<tt>sane_close()</tt>. Finally, before exiting the application,
function <tt>sane_exit()</tt> must be called. It is important not to
forget to call this function since otherwise some resources (e.g.,
temporary files or locks) may remain unclaimed.
<p><font color="darkgreen">
The following C sample code implements a reference loop for acquiring
multiple images:
<p><pre>
SANE_Parameters parms;
SANE_Status status;
do
{
do
{
/* Now start acquiring the next frame. */
status = sane_start (handle);
/* if that failed, we have a problem, and no more frames can be
* read at this time. Due to SANE_PFLAG_MORE_IMAGES still
* being clear, this will break out of _BOTH_ loops.
*/
if (status != SANE_STATUS_GOOD)
break;
/* Now let us see what the next frame brings. */
status = sane_get_parameters (handle, &amp;parms);
/* This actually should not fail, but maybe the doc feeder
* jammed or something, so we break as well, if something
* is wrong.
*/
if (status != SANE_STATUS_GOOD)
break;
/* Now we check the announced parameters, if we can make use
* of the frame data. If not, we skip over to the next frame.
*/
if (do_i_like_that (&amp;parms) == NO)
continue;
/* Set up for reading the data here. Mangle filenames,
* allocate memory, rewind multiframe files, ask user
* for confirmation, ...
*/
setup_for_transfer (...);
/* Now we read in the frame data and process it. This should
* return SANE_STATUS_GOOD, until the frame is complete,
* what causes SANE_STATUS_EOF to be returned.
*/
while (SANE_STATUS_GOOD == (status = sane_read (...)))
read_in_and_process_data_as_required ();
/* If transfer was broken due to anything but EOF, break out. */
if (status != SANE_STATUS_EOF)
break;
/* Now loop until we have all frames of an image. */
}
while (!(parms.flag &amp; SANE_PFLAG_LAST_FRAME));
/* O.K. - we now have a complete image. Fit it together, save it,
* flush buffers, transmit it, increment filenames, etc.
*/
/* Now check for more pending images. If we have more, redo from start.
* Some backends might cheat here and send us for an extra round which
* will fail at sane_start, as they were not able to determine if they
* would have more data at the start of the last frame we read.
*/
}
while (parms.flags &amp; SANE_PFLAG_MORE_IMAGES);
/* No more data. Fine. Reset the backend and go back to option-control
* loop.
*/
sane_cancel (handle);
</pre>
<p></font>
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<hr>
<title>Well-Known Options</title>
<h2><a name="s4.5">4.5 Well-Known Options</a></h2><a name="i118">
<p>While most backend options are completely self-describing, there are
cases where a user interface might want to special-case the handling
of certain options. For example, the scan area is typically defined
by four options that specify the top-left and bottom-right corners of
the area. With a graphical user interface, it would be tedious to
force the user to type in these four numbers. Instead, most such
interfaces will want to present to the user a preview (low-resolution
scan of the full scanner surface or a high(er) resolution scan of a subpart
of the scanner surface) and let the user pick the scan area by
dragging a rectangle into the desired position. For this reason, the
SANE API specifies a small number of option names that have
well-defined meanings.
<p><h3><a name="s4.5.1">4.5.1 Option Number Count</a></h3><a name="i119">
<p>Option number 0 has an empty string as its name. The value of this
option is of type <tt>SANE_TYPE_INT</tt> and it specifies the total
number of options available for a given device (the count includes
option number 0). This means that there are two ways of counting the
number of options available: a frontend can either cycle through all
option numbers starting at one until
<tt>sane_get_option_descriptor()</tt> returns <tt>NULL</tt>, or a
frontend can directly read out the value of option number 0.
<p><h3><a name="s4.5.2">4.5.2 Scan Resolution Options</a></h3><a name="i120"><a name="i121">
<p>Option <tt>resolution</tt> is used to select the resolution at which an
image should be acquired.
<font color="darkgreen">
When the backend wants to allow different
values for x- and y-resolution it has to define the options
<tt>x-resolution</tt> and <tt>y-resolution</tt>. Note that only
the option <tt>resolution</tt> <b>or</b> the options
<tt>x-resolution</tt> <b>and</b> <tt>y-resolution</tt> may be active at the
same time.
</font>
<p>The type of this option is either <tt>SANE_TYPE_INT</tt> or
<tt>SANE_TYPE_FIXED</tt>. The unit is <tt>SANE_UNIT_DPI</tt> (dots/inch).
<p>These options are not mandatory, but if a backend does support them, it
must implement them in a manner consistent with the above definition.
<p><h3><a name="s4.5.3">4.5.3 Preview Mode Option</a></h3><a name="i122">
<p>The boolean option <tt>preview</tt> is used by a frontend to inform the
backend when image acquisition should be optimized for speed, rather
than quality (``preview mode''). When set to <tt>SANE_TRUE</tt>,
preview mode is in effect, when set to <tt>SANE_FALSE</tt> image
acquisition should proceed in normal quality mode. The setting of
this option <em>must not</em> affect any other option. That is, as
far as the other options are concerned, the preview mode is completely
side effect free. A backend can assume that the frontend will take
care of appropriately setting the scan resolution for preview mode
(through option <tt>resolution</tt>). A backend is free to override the
<tt>resolution</tt> value with its own choice for preview mode, but it
is advised to leave this choice to the frontend wherever possible.
<font color="darkgreen">
When the <tt>preview</tt> option is set the backend should transfer
the image in frame type <tt>SANE_FRAME_RAW</tt> if possible.
</font>
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
<p><h3><a name="s4.5.4">4.5.4 Scan Area Options</a></h3><a name="i123">
<p>The four most important well-known options are the ones that define
the scan area. The scan area is defined by two points (x/y coordinate
pairs) that specify the top-left and the bottom-right corners. This
is illustrated in Figure <a href="doc014.html#f5">5</a>. Note that the origin of the
coordinate system is at the top-left corner of the scan surface as
seen by the sensor (which typically is a mirror image of the scan
surface seen by the user). For this reason, the top-left corner is
the corner for which the abscissa and ordinate values are
simultaneously the <em>smallest</em> and the bottom-right corner is the
corner for which the abscissa and ordinate values are simulatenously
the <em>largest</em>. If this coordinate system is not natural for a
given device, it is the job of the backend to perform the necessary
conversions.
<p><a name="f5"></a>
<center>
<img width=330 height=306 src="img004.gif">
<p><center>Figure 5: Scan area options</center>
</center>
<p>
<p>The names of the four options that define the scan area are given in
the table below:
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>Name</b> </td>
<td colspan=1 align=left nowrap> <b>Description</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>tl-x<a name="i124"></tt> </td>
<td colspan=1 align=left nowrap> Top-left x coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>tl-y<a name="i125"></tt> </td>
<td colspan=1 align=left nowrap> Top-left y coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>br-x<a name="i126"></tt> </td>
<td colspan=1 align=left nowrap> Bottom-right x coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>br-y<a name="i127"></tt> </td>
<td colspan=1 align=left nowrap> Bottom-right y coordinate value </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
There are several rules that should be followed by front and backends
regarding these options:
<ul>
<p><li>Backends must attach a unit of either pixels
(<tt>SANE_UNIT_PIXEL</tt>) or millimeters (<tt>SANE_UNIT_MM</tt>) to
these options. The unit of all four options must be identical.
<p><li>Whenever meaningful, a backend should attach a range or a
word-list constraint to these options.
<p><li>A frontend can determine the size of the scan surface by first
checking that the options have range constraints associated. If a
range or word-list constraints exist, the frontend can take the
minimum and maximum values of one of the x and y option
range-constraints to determine the scan surface size.
<p><li>A frontend must work properly with any or all of these options
missing.
<font color="darkgreen">
<li>A frontend may temporarily set the values in a way that
<tt>tl-x</tt> is larger than <tt>br-x</tt> and <tt>tl-y</tt> is larger than
<tt>br-y</tt>.
</font>
<p></ul>
<p><font color="darkgreen">
These options are not mandatory, but if a backend does support them, it
must implement them in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.5">4.5.5 Depth Option</a></h3><a name="i128">
Option <tt>depth</tt> is used to select the image depth in bits/sample
in multi bit mode (e.g. for 24 bit RGB mode this value must be 8).
The type of this option is <tt>SANE_TYPE_INT</tt>.
The unit is <tt>SANE_UNIT_BIT</tt>. For 1 bit modes
(Lineart or Halftone) this option has to be inactive.
For selection of 1 bit modes (Lineart or Halftone) the
backend should use the well-known option <tt>mode</tt>.
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<font color="darkgreen">
<h3><a name="s4.5.6">4.5.6 Scan Mode Options</a></h3><a name="i129">
The option <tt>mode</tt> defines a <tt>SANE_CONSTRAINT_STRING_LIST</tt>
of type <tt>SANE_TYPE_STRING</tt>.
It is used to select the scanmode (e.g. Color or Gray).
Well known modes are: <tt>Color</tt>, <tt>Gray</tt>, <tt>Halftone</tt>
and <tt>Lineart</tt>. <tt>Color</tt> and <tt>Gray</tt> are multi bit
modes (8 or 16 bits/sample), <tt>Halftone</tt> and <tt>Lineart</tt>
are single bit modes. When well-known scan modes are used,
a frontend is able to automatically decide which mode is appropriate
for a specific task, e.g the mode <tt>Gray</tt>
for scanning a fax.
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<font color="darkgreen">
<h3><a name="s4.5.7">4.5.7 Scan Source Options</a></h3><a name="i130">
The option <tt>source</tt> is used to select the scan source
(e.g. Automatic Document Feeder).
It defines a <tt>SANE_CONSTRAINT_STRING_LIST</tt>
of type <tt>SANE_TYPE_STRING</tt>.
Well known sources are: <tt>Flatbed</tt>, <tt>Transparancy Adapter</tt> and
<tt>Automatic Document Feeder</tt>.
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.8">4.5.8 Threshold Option</a></h3><a name="i131">
The option <tt>threshold</tt> is used to define the threshold
for Lineart and maybe Halftone mode. In multi bit modes
this option should be set inactive.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_PERCENT</tt>. The value range
should be 0.0...100.0 if possible.
It defines the minimum intensity to get a white point / full intensity.
<p>The backend has to scale the values in the following way:
A value of 0.0 means all pixels get white / full intensity. A value of 50.0
means intensities brighter than medium gray get white / full intensity. A
value of 100.0 means all pixels get black. If the
scanner is not able to cover the full range the backend has to define a
reduced value range (e.g. 30...70 percent).
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.9">4.5.9 Gamma Table Options</a></h3><a name="i132">
The <tt>gamma-table</tt> option defines a <tt>SANE_CONSTRAINT_RANGE</tt>
of the type <tt>SANE_TYPE_INT</tt> which represents the gamma correction
table for gray. In color mode the <tt>gamma-table</tt> may be used to set
a common gamma correction for red, green and blue. The options
<tt>red-gamma-table</tt>, <tt>green-gamma-table</tt> and <tt>blue-gamma-table</tt>
are used in color mode to set a gamma correction for each color
separately. In color mode the backend is free to use only the
<tt>gamma-table</tt> option, only the <tt>red-</tt>, <tt>green-</tt> and
<tt>blue-gamma-table</tt> or all four options. When all four options
are used then the color tables should do a gamma correction with
the same input and output bit depth and the gray gamma table should
reduce (if necessary) the bit depth from the scanner internal
bit depth to the output bit depth. This should e.g. look like this:
<pre>
red_value = gamma-table(red-gamma-table(value))
green_value = gamma-table(green-gamma-table(value))
blue_value = gamma-table(blue-gamma-table(value))
</pre>
<p>The backend should not use the gamma tables to emulate other functions or options
like highlight, shadow, contrast, brightness, threshold, analog_gamma.
These functions are common for all backends and should be added to the frontend
or a meta-backend.
<p>It is also discouraged to emulate gamma tables in the backend. The backend
should disable (or not define) this option when the scanner does not support
gamma tables in hardware.
This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.10">4.5.10 Analog Gamma</a></h3><a name="i133">
The option <tt>analog-gamma</tt> is used to define the gamma value
for an analog gamma function of the scanner in multi bit modes.
In 1 bit modes this option should be set inactive.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_NONE</tt>. The value range
can be defined by the backend as supported. The values
have to be positive. A gamma value of 1.0 means that
the gamma correction has no effect. A value larger than
1.0 increases the brightness of the image.
In color mode there also can be options <tt>analog-gamma-red</tt>,
<tt>analog-gamma-green</tt> and <tt>analog-gamma-blue</tt>.
It is not allowed to emulate an analog gamma function by
a digital gamma table. The backend has to disable (or not
define) this option when the scanner does not support an
analog (hardware) gamma function.
<p>When analog gamma, highlight and shadow functions are available
at the same time then the backend author has to care about the order
in which the functions are implemented in the scanner hardware.
The SANE standard expects that changing the analog gamma value
has no effect on the shadow and highlight function. When the
analog gamma function is executed in the scanner hardware
before the shadow and highlight functions then the backend
should do a compensation. For this the shadow and highlight
values have to be gamma corrected with the relevant analog gamma value.
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.11">4.5.11 Shadow Option</a></h3><a name="i134">
The option <tt>shadow</tt> is used to define the shadow level / black point level.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_PERCENT</tt>. The value range
should be 0.0...100.0 if possible.
It is used to define the maximum intensity level that creates an image data value
of 0 (black).
<p>The backend has to scale the values in the following way:
A value of 0.0 means that the sensitivity range is not reduced, only the
minimum intensity produces an image data value of 0 (black).
A value of 50.0 means that that a medium intensity and everything that is darker
produces an image data value of 0 (black).
A value of 100.0 means the sensitivity range is reduced to 0, all image
data values are 0 (black). If the scanner is not able to
cover the full range the backend has to define a reduced
value range (e.g. 30...70 percent).
In color mode there can be options <tt>shadow-red</tt>, <tt>shadow-green</tt>
and <tt>shadow-blue</tt>, in this case the <tt>shadow</tt> function has to be disabled.
It is not allowed to emulate a shadow function by
a digital gamma table. The backend has to disable (or not
define) this option when the scanner does not support an
analog (hardware) shadow function.
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.12">4.5.12 Highlight Option</a></h3><a name="i135">
The option <tt>highlight</tt> is used to define the highlight level / white point level.
The type of this option is <tt>SANE_TYPE_FIXED</tt>.
The unit is <tt>SANE_UNIT_PERCENT</tt>. The value range
should be 0.0...100.0 if possible.
It is used to define the minimum intensity level that creates the maximum possible
image data value (white/full intensity).
<p>The backend has to scale the values in the following way:
A value of 0.0 means the sensitivity range is reduced to 0, all image
data have maximum value (white / full intensity).
A value of 50.0 means that a medium intensity and everything that is brighter
produces the maximum possible image data value (white / full intensity).
A value of 100.0 means that the sensitivity range is not reduced, only the
maximum intensity produces an image data with maximum possible value (white / full intensity).
If the scanner is not able to cover the full range the backend has to define a reduced
value range (e.g. 30...70 percent).
In color mode there can be options <tt>highlight-red</tt>, <tt>highlight-green</tt>
and <tt>highlight-blue</tt>, in this case <tt>highlight</tt> has to be disabled.
It is not allowed to emulate a highlight function by
a digital gamma table. The backend has to disable (or not
define) this option when the scanner does not support an
analog (hardware) highlight function.
<p>This option is not mandatory, but if a backend does support it, it
must implement it in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.13">4.5.13 Lamp Options</a></h3><a name="i136"><a name="i137">
<p>The options <tt>lamp-on</tt> and <tt>lamp-off</tt> are button options
(<tt>SANE_TYPE_BUTTON</tt>) and don't have a unit (<tt>SANE_UNIT_NONE</tt>).
<p>Option <tt>lamp-on</tt> is used to turn on the lamp of the scanner while
<tt>lamp-off</tt> turns it off.
<p>These options are not mandatory, but if a backend does support them, it
must implement them in a manner consistent with the above definition.
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.14">4.5.14 Scanner Button Options</a></h3><a name="i138">
Some scanners have buttons which state can be read by the scanner driver.
It is necessary to implement a locking function for the buttons
because it is possible that several frontends try to connect to the
same backend/scanner at the same time. Imagine what could happen
when no locking would be implemented:
Five people have started a scanning application which is connected
via network to the scanner you want to use. You start a frontend,
put a paper to the scanner and press the scan-button on the scanner.
The scanner does scan three times (because three frontends asked the
button status when you pressed the button). For three people the
image is saved to the harddisk, but it is not sure that your
frontend did scan the image.
<p>A backend that does make available the scanner-buttons has to
implement the following options:<br>
<tt>scanner-buttons-lock</tt> is of type <tt>SANE_TYPE_BOOL</tt>, default = <tt>SANE_FALSE</tt><br>
<tt>scanner-buttons-status</tt> is of type <tt>SANE_TYPE_INT</tt>, default = 0<br>
<tt>scanner-buttons-status-update</tt> is of type <tt>SANE_TYPE_BUTTON</tt><br>
When setting these options the backend does not set <tt>SANE_INFO_RELOAD_OPTIONS</tt>
or <tt>SANE_INFO_RELOAD_PARAMS</tt> if not explictly defined.
<p>A frontend has to disable the usage of the scanner-buttons by default. This is important
because other frontends will not be able to use the buttons when the button-functions are locked.
Another important thing is that some scanners do not turn off their lamp when the driver
does frequently talk to the scanner (what is done when reading the button status from the scanner).
<p><ul>
<p><li>
A frontend that wants to read the button status has to lock the
button functions at first. For this it does set the option
<tt>scanner-buttons-lock</tt> to <tt>SANE_TRUE</tt>.
While setting the value of option <tt>scanner-buttons-lock</tt> to <tt>SANE_TRUE</tt>
the backend does check if a lockfile (e.g. ``backend''-buttons.lock) does exist.
The lockfile has to be placed in a directory where every user has read and write access to.
<p> <ul>
<li>
If the lockfile does not exist then the backend creates the lockfile and writes the
process ID (PID) of the backend to the file. Button access is allowed: the value
of option <tt>scanner-buttons-lock</tt> is set to <tt>SANE_TRUE</tt>
<li>
If the file does exist and the backend PID is not the file PID then the
backend has to check if the process with the PID stored in the lockfile
still is running. If yes then the button access is not allowed: the value of
option <tt>scanner-buttons-lock</tt> is set to <tt>SANE_FALSE</tt>. If not then the lockfile
is recreated and the PID of the backend is stored in the lockfile, button
access is allowed: the value of option <tt>scanner-buttons-lock</tt> is set to <tt>SANE_TRUE</tt>
</ul>
<p><li>
The frontend does read the value of option <tt>scanner-buttons-lock</tt>. If
it is <tt>SANE_TRUE</tt> then the frontend has access to the scanner buttons.
If it is <tt>SANE_FALSE</tt> then access has been denied.
<p><li>
If the button access is allowed the frontend has to do the following about
once per second (while not scanning):
<ul>
<li>
The frontend does set option <tt>scanner-buttons-status-update</tt>.
The backend checks if access to the buttons is allowed by comparing
the backend PID with the lockfile PID. If access is allowed it
does read the button status from the scanner and stores it in
the option <tt>scanner-buttons-status</tt>, each bit represents a button, a
value of 0 means the button is not pressed, a value of 1 means that the button
is pressed. When the scanner is busy the backend must not wait, it has to
return immediately and the button state keeps unchanged.
The backend has to implement a timeout function. When no button has been pressed
within a predefined time (e.g. 15 minutes) then the access permission is lost.
In this case the backend does set option <tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>
and does set <tt>SANE_INFO_RELOAD_OPTIONS</tt> to inform the frontend that it has
lost permission to access the scanner-button functions.
If access is not allowed it does set the <tt>scanner-buttons-status</tt> to 0.
<p> <li>
The frontend does read the value of option <tt>scanner-buttons-status</tt>
</ul>
<p><li>
When the frontend does exit or it does not want to use the buttons
it does set option <tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>.
The backend does check if the backend PID and the lockfile PID are
the same. If this is true then it removes the lockfile and sets the value
of <tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>.
<p><tt>sane_close()</tt> should do the same as setting option
<tt>scanner-buttons-lock</tt> to <tt>SANE_FALSE</tt>.
<p></ul>
</font>
<p><font color="darkgreen">
<h3><a name="s4.5.15">4.5.15 Batch Scan Options</a></h3><a name="i139">
<p>The batch scan options can be used by a frontend to indicate that more than
one image will be scanned in a batch. The backend can optimize for such scans
by e.g. avoiding calibration and not moving home the sensor array in this case.
The backend provides the options <tt>batch-scan</tt>,
<tt>batch-scan-next-tl-x</tt>, <tt>batch-scan-next-tl-y</tt>,
<tt>batch-scan-next-br-x</tt>, and <tt>batch-scan-next-br-y</tt>. The option
<tt>batch-scan</tt> provides a string list with the values of <tt>No</tt> if
batch scanning isn't used, <tt>Start</tt> for the first, <tt>End</tt> for the last
and <tt>Loop</tt> for any other (intermediate) image. The batch-scan-next
options specify the coordinates of the next scan and follow the same rules as
the scan area options (see section <a href="doc014.html#s4.5.4">4.5.4</a>).
<p>These options are not mandatory, but if a backend does support them, it must
implement them in a manner consistent with the above definition. In this
case, all options must be implemented.
</font>
<p><p><hr>
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<hr>
<title>Network Protocol</title>
<h1><a name="s5">5 Network Protocol</a></h1>
<p>The SANE interface has been designed to facilitate network access to
image acquisition devices. In particular, most SANE implementations
are expected to support a network backend (net client) and a
corresponding network daemon (net server) that allows accessing image
acquisition devices through a network connection. Network access is
useful in several situations:
<ul>
<p><li>To provide controlled access to resources that are inaccessible
to a regular user. For example, a user may want to access a device
on a host where she has no account on. With the network protocol,
it is possible to allow certain users to access scanners without
giving them full access to the system.
<p> Controlling access through the network daemon can be useful even in
the local case: for example, certain backends may require root
privileges to access a device. Rather than installing each frontend
as setuid-root, a system administrator could instead install the
SANE network daemon as setuid-root. This enables regular users to
access the privileged device through the SANE daemon (which,
presumably, supports a more fine-grained access control mechanism
than the simple setuid approach). This has the added benefit that
the system administrator only needs to trust the SANE daemon, not
each and every frontend that may need access to the privileged
device.
<p><li>Network access provides a sense of ubiquity of the available
image acquisition devices. For example, in a local area network
environment, this allows a user to log onto any machine and have
convenient access to any resource available to any machine on the
network (subject to permission constraints).
<p><li>For devices that do not require physical access when used (e.g.,
video cameras), network access allows a user to control and use
these devices without being in physical proximity. Indeed, if such
devices are connected to the Internet, access from any place in the
world is possible.
<p></ul>
<p>The network protocol described in this chapter has been design with
the following goals in mind:
<ol>
<p><li>Image transmission should be efficient (have low encoding
overhead).
<p><li>Accessing option descriptors on the client side must be
efficient (since this is a very common operation).
<p><li>Other operations, such as setting or inquiring the value of an
option are less performance critical since they typically require
explicit user action.
<p><li>The network protocol should be simple and easy to implement on
any host architecture and any programming language.
<p></ol>
The SANE protocol can be run across any transport protocol that
provides reliable data delivery. While SANE does not specify a
specific transport protocol, it is expected that TCP/IP will be among
the most commonly used protocols.
<p><h2><a href="doc016.html">5.1 Data Type Encoding</a></h2><h2><a href="doc017.html">5.2 Remote Procedure Call Requests</a></h2><p><hr>
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<title>Data Type Encoding</title>
<h2><a name="s5.1">5.1 Data Type Encoding</a></h2>
<p><h3><a name="s5.1.1">5.1.1 Primitive Data Types</a></h3>
<p>The four primitive types of the SANE standard are encoded as follows:
<dl>
<p><dt><tt>SANE_Byte<a name="i140"></tt>:<dd> A byte is encoded as an 8 bit value.
Since the transport protocol is assumed to be byte-orientd, the bit
order is irrelevant.
<p><dt><tt>SANE_Word<a name="i141"></tt>:<dd> A word is encoded as 4 bytes (32
bits). The bytes are ordered from most-significant to
least-significant byte (big-endian byte-order).
<p><dt><tt>SANE_Char<a name="i142"></tt>:<dd> A character is currently encoded as an 8-bit
ISO LATIN-1 value. An extension to support wider character sets (16 or 32
bits) is planned for the future, but not supported at this point.
<p><dt><tt>SANE_String<a name="i143"></tt>:<dd> A string pointer is encoded as a
<tt>SANE_Char</tt> array. The trailing NUL byte is considered part
of the array and a <tt>NULL</tt> pointer is encoded as a zero-length
array.
<dt><tt>SANE_Handle<a name="i144"></tt>:<dd> A handle is encoded like a word.
The network backend needs to take care of converting these integer
values to the opaque pointer values that are presented to the user
of the network backend. Similarly, the SANE daemon needs to take
care of converting the opaque pointer values it receives from its
backends into 32-bit integers suitable for use for network encoding.
<p><dt><em>enumeration types<a name="i145"></em>:<dd> Enumeration types are encoded
like words.
<p></dl>
<p><h3><a name="s5.1.2">5.1.2 Type Constructors</a></h3>
<p>Closely following the type constructors of the C language, the SANE network
protocol supports the following four constructors:
<dl>
<p><dt><em>pointer<a name="i146"></em>:<dd> A pointer is encoded by a word that indicates
whether the pointer is a NULL-pointer which is then followed by the
value that the pointer points to (in the case of a non-NULL pointer;
in the case of a NULL pointer, no bytes are encoded for the pointer
value).
<p><dt><em>array<a name="i147"></em>:<dd> An array is encoded by a word that indicates
the length of the array followed by the values of the elements in
the array. The length may be zero in which case no bytes are
encoded for the element values.
<p><dt><em>structure<a name="i148"></em>:<dd> A structure is encoded by simply encoding the
structure members in the order in which they appear in the
corresponding C type declaration.
<p><dt><em>union<a name="i149"></em>:<dd> A union must always be accompanied by a tag
value that indicates which of the union members is the currently the
active one. For this reason, the union itself is encoded simply by
encoding the value of the currently active member.
<p></dl>
<p>Note that for type constructors, the pointer, element, or member
values themselves may have a constructed type. Thus, the above rules
should be applied recursively until a sequence of primitive types has
been found.
<p>Also SANE had no need for encoding of circular structures. This
greatly simplifies the network protocol.
<p><p><hr>
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<hr>
<title>Remote Procedure Call Requests</title>
<h2><a name="s5.2">5.2 Remote Procedure Call Requests</a></h2>
<p>The SANE network protocol is a client/server-style remote procedure
call (RPC) protocol. This means that all activity is initiated by the
client side (the network backend)---a server is restricted to
answering request by the client.
<p><h3><a name="s5.2.1">5.2.1 <tt>SANE_NET_INIT<a name="i150"></tt></a></h3>
<p>This RPC establishes a connection to a particular SANE network daemon.
It must be the first call in a SANE network session. The parameter
and reply arguments for this call are shown in the table below:
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word version_code</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String user_name</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word version_code</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>version_code</tt> argument in the request is the SANE
version-code of the network backend that is contacting the network
daemon (see Section <a href="doc010.html#s4.1">4.1</a>). The
``build-revision'' in the version code is used to hold the network
protocol version. The SANE network daemon receiving such a request
must make sure that the network protocol version corresponds to a
supported version since otherwise the encoding of the network stream
may be incompatible (even though the SANE interface itself may be
compatible). The <tt>user_name</tt> argument is the name of the user
on whose behalf this call is being performed. If the network backend
cannot determine a user-name, it passes a <tt>NULL</tt> pointer for this
argument. No trust should be placed in the authenticity of this
user-name. The intent of this string is to provide more convenience
to the user. E.g., it could be used as the default-user name in
subsequent authentication calls.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values.<a name="F2"><a href="footnotes.html#000002"><sup><fontsize=-2>2</font></sup></a></a> The <tt>version_code</tt> argument returns the
SANE version-code that the network daemon supports. See the comments
in the previous paragraph on the meaning of the build-revision in this
version code.
<p><h3><a name="s5.2.2">5.2.2 <tt>SANE_NET_GET_DEVICES<a name="i152"></tt></a></h3>
<p>This RPC is used to obtain the list of devices accessible by the SANE
daemon.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>void</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Device ***device_list</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
There are no arguments in the request for this call.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values. The <tt>device_list</tt>
argument is a pointer to a <tt>NULL</tt>-terminated array of
<tt>SANE_Device</tt> pointers.
<p><h3><a name="s5.2.3">5.2.3 <tt>SANE_NET_OPEN<a name="i154"></tt></a></h3>
<p>This RPC is used to open a connection to a remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String device_name</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Word handle</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_String resource</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>device_name</tt> argument specifies the name of the device to
open.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values. The <tt>handle</tt>
argument specifies the device handle that uniquely identifies the
connection. The <tt>resource</tt> argument is used to request
authentication. If it has a non-<tt>NULL</tt> value, the network
backend should authenticate the specified resource and then retry this
operation (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
authorize a resource).
<p><h3><a name="s5.2.4">5.2.4 <tt>SANE_NET_CLOSE<a name="i156"></tt></a></h3>
<p>This RPC is used to close a connection to a remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection that should be
closed.
<p>In the reply, the <tt>dummy</tt> argument is unused. Its purpose is to
ensure proper synchronization (without it, a net client would not be
able to determine when the RPC has completed).
<p><h3><a name="s5.2.5">5.2.5 <tt>SANE_NET_GET_OPTION_DESCRIPTORS<a name="i158"></tt></a></h3>
<p>This RPC is used to obtain <em>all</em> the option descriptors for a
remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>Option_Descriptor_Array odesc</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the remote device whose option
descriptors should be obtained.
<p>In the reply, the <tt>odesc</tt> argument is used to return the array of
option descriptors. The option descriptor array has the following
structure:
<blockquote><a name="i160">
<pre>
struct Option_Descriptor_Array
{
SANE_Word num_options;
SANE_Option_Descriptor **desc;
};
</pre>
</blockquote>
<p><h3><a name="s5.2.6">5.2.6 <tt>SANE_NET_CONTROL_OPTION<a name="i161"></tt></a></h3>
<p>This RPC is used to control (inquire, set, or set to automatic) a
specific option of a remote SANE device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word option</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word info</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word action</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word value_type</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word value_type</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word value_size</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word value_size</tt> </td>
<td colspan=1 align=left nowrap> <tt>void *value</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>void *value</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_String *resource</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the remote device whose option
should be controlled. Argument <tt>option</tt> is the number (index) of
the option that should be controlled. Argument <tt>action</tt>
specifies what action should be taken (get, set, or set automatic).
Argument <tt>value_type</tt> specifies the type of the option value
(must be one of <tt>SANE_TYPE_BOOL</tt>, <tt>SANE_TYPE_INT</tt>,
<tt>SANE_TYPE_FIXED</tt>, <tt>SANE_TYPE_STRING</tt>,
<tt>SANE_TYPE_BUTTON</tt>). Argument <tt>value_size</tt> specifies
the size of the option value in number of bytes (see
Section <a href="doc011.html#s4.2.9.6">4.2.9.6</a> for the precise meaning of this value).
Finally, argument <tt>value</tt> is a pointer to the option value. It
must be a writeable area that is at least <tt>value_size</tt> bytes
large. (Note that this area must be writable even if the action is to
set the option value. This is because the backend may not be able to
set the exact option value, in which case the option value is used to
return the next best value that the backend has chosen.)
<p>In the reply, argument <tt>resource</tt> is set to the name of the
resource that must be authorized before this call can be retried. If
this value is non-<tt>NULL</tt>, all other arguments have undefined
values (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
authorize a resource). Argument <tt>status</tt> indicates the
completion status. If the value is anything other than
<tt>SANE_STATUS_SUCCESS</tt>, the remainder of the reply has undefined
values. The <tt>info</tt> argument returns the information on how well
the backend was able to satisfy the request. For details, see the
description of the corresponding argument in
Section <a href="doc012.html#s4.3.7">4.3.7</a>. Arguments <tt>value_type</tt> and
<tt>value_size</tt> have the same values as the arguments by the same
name in corresponding request. The values are repeated here to ensure
that both the request and the reply are self-contained (i.e., they can
be encoded and decoded independently). Argument <tt>value</tt> is holds
the value of the option that has become effective as a result of this
RPC.
<p><h3><a name="s5.2.7">5.2.7 <tt>SANE_NET_GET_PARAMETERS<a name="i163"></tt></a></h3>
<p>This RPC is used to obtain the scan parameters of a remote SANE
device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Parameters params</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection to the remote
device whose scan parameters should be returned.
<p>In the reply, <tt>status</tt> indicates the completion status. If the
value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
remainder of the reply has undefined values. The argument
<tt>params</tt> is used to return the scan parameters.
<p><h3><a name="s5.2.8">5.2.8 <tt>SANE_NET_START<a name="i165"></tt></a></h3>
<p>This RPC is used to start image acquisition (scanning).
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Word port</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_Word byte_order</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td>
<td colspan=1 align=left nowrap> <tt>SANE_String resource</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection to the remote
device from which the image should be acquired.
<p>In the reply, argument <tt>resource</tt> is set to the name of the
resource that must be authorized before this call can be retried. If
this value is non-<tt>NULL</tt>, all other arguments have undefined
values (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
authorize a resource). Argument, <tt>status</tt> indicates the
completion status. If the value is anything other than
<tt>SANE_STATUS_SUCCESS</tt>, the remainder of the reply has
undefined values. The argument <tt>port</tt> returns the port number
from which the image data will be available. To read the image data,
a network client must connect to the remote host at the indicated port
number. Through this port, the image data is transmitted as a
sequence of data records. Each record starts with the data length in
bytes. The data length is transmitted as a sequence of four bytes.
These bytes should be interpreted as an unsigned integer in big-endian
format. The four length bytes are followed by the number of data
bytes indicated by the length. Except for byte-order, the data is in
the same format as defined for <tt>sane_read()</tt>. Since some
records may contain no data at all, a length value of zero is
perfectly valid. The special length value of <tt>0xffffffff</tt> is
used to indicate the end of the data stream. That is, after receiving
a record length of <tt>0xffffffff</tt>, the network client should close
the data connection and stop reading data.
<p>Argument <tt>byte_order</tt> specifies the byte-order of the image
data. A value of 0x1234 indicates little-endian format, a value of
0x4321 indicates big-endian format. All other values are presently
undefined and reserved for future enhancements of this protocol. The
intent is that a network server sends data in its own byte-order and
the client is responsible for adjusting the byte-order, if necessary.
This approach causes no unnecessary overheads in the case where the
server and client byte-order match and puts the extra burden on the
client side when there is a byte-order mismatch. Putting the burden
on the client-side improves the scalability properties of this
protocol.
<p><h3><a name="s5.2.9">5.2.9 <tt>SANE_NET_CANCEL<a name="i167"></tt></a></h3>
<p>This RPC is used to cancel the current operation of a remote SANE
device.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_Word handle</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>handle</tt> argument identifies the connection whose operation
should be cancelled.
<p>In the reply, the <tt>dummy</tt> argument is unused. Its purpose is to
ensure proper synchronization (without it, a net client would not be
able to determine when the RPC has completed).
<p><h3><a name="s5.2.10">5.2.10 <tt>SANE_NET_AUTHORIZE<a name="i169"></tt></a></h3>
<a name="i171">
<p>This RPC is used to pass authorization data from the net client to the
net server.
<center>
<table cellpadding=0 cellspacing=0>
<tr valign=top>
<td colspan=1 align=left nowrap>
<b>request:</b> </td>
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String resource</tt> </td>
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String username</tt> </td>
<td colspan=1 align=left nowrap> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
<tt>SANE_String password</tt> </td>
<td colspan=1 align=left nowrap> </td></tr>
<tr valign=top>
<td colspan=1 align=left nowrap>
</td></tr>
</table>
</center>
The <tt>resource</tt> argument specifies the name of the resource to be
authorized. This argument should be set to the string returned in the
<tt>resource</tt> argument of the RPC reply that required this
authorization call. The <tt>username</tt> and <tt>password</tt> are the
name of the user that is accessing the resource and the password for
the specified resource/user pair.
<p>Since the password is not encrypted during network transmission, it is
recommended to use the following extension:
<p>If the server adds the string `<tt>$MD5$</tt>' to the resource-name followed
by a random string not longer then 128 bytes, the client may answer with the
MD5 digest of the concatenation of the password and the random string. To
differentiate between the MD5 digest and a strange password the client prepends
the MD5 digest with the string `<tt>$MD5$</tt>'.
<p>In the reply, <tt>dummy</tt> is completely unused. Note that there is
no direct failure indication. This is unnecessary since a net client
will retry the RPC that resulted in the authorization request until
that call succeeds (or until the request is cancelled). The RPC that resulted
in the authorization request continues after the reply from the client and may
fail with <tt>SANE_STATUS_ACCESS_DENIED</tt>.
<p><h3><a name="s5.2.11">5.2.11 <tt>SANE_NET_EXIT<a name="i172"></tt></a></h3>
<p>This RPC is used to disconnect a net client from a net server. There
are no request or reply arguments in this call. As a result of this
call, the connection between the client and the server that was
established by the <tt>SANE_NET_INIT</tt> call will be closed.
<p>
<p><p><hr>
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<hr>
<title>Contact Information</title>
<h1><a name="s6">6 Contact Information</a></h1>
<p>The SANE standard is discussed and evolved via a mailing list.
Anybody with email access to the Internet can automatically join and
leave the discussion group by sending mail to the following address.
<blockquote><a name="i174">
<pre>
sane-devel-request@mostang.com
</pre>
</blockquote>
To subscribe, send a mail with the body ``<tt>subscribe sane-devel</tt>'' to the
above address.
<p>A complete list of commands supported can be obtained by sending a
mail with a subject of ``<tt>help</tt>'' to the above address. The
mailing list is archived and available through the SANE home page at
URL:
<blockquote>
<a href="http://www.mostang.com/sane/">http://www.mostang.com/sane/</a>
</blockquote>
<p>
<p>
<p><hr>
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<html><body>
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<hr>
<h1>Index</h1>
<p><multicol cols=2>
<p><a href="doc014.html#i133">analog gamma option</a><br>
<a href="doc016.html#i147">array</a><br>
<p><a href="doc014.html#i139">Batch Scan Options</a><br>
<a href="doc014.html#i128">bit depth option</a><br>
<a href="doc014.html#i126">br-x</a><br>
<a href="doc014.html#i127">br-y</a><br>
<p><a href="doc013.html#i117">code flow</a><br>
<p><a href="doc011.html#i43">device-name</a><br>
<a href="doc012.html#i82">domain</a><br>
<p><a href="doc016.html#i145">enumeration types</a><br>
<p><a href="doc014.html#i132">gamma table options</a><br>
<p><a href="doc014.html#i135">hightlight options</a><br>
<p><a href="doc008.html#i0">image data format</a><br>
<p><a href="doc014.html#i137">lamp-off option</a><br>
<a href="doc014.html#i136">lamp-on option</a><br>
<p><a href="doc018.html#i174">mailing list</a><br>
<a href="doc014.html#i129">mode options</a><br>
<p><a href="doc017.html#i171">network authorization</a><br>
<a href="doc011.html#i26">NUL</a><br>
<p><a href="doc014.html#i119">option count</a><br>
<a href="doc017.html#i160">Option_Descriptor_Array</a><br>
<p><a href="doc012.html#i84">password</a><br>
<a href="doc016.html#i146">pointer</a><br>
<a href="doc014.html#i122">preview mode</a><br>
<p><a href="doc014.html#i121">resolution option</a><br>
<p><a href="doc012.html#i91">SANE_Action</a><br>
<a href="doc012.html#i92">SANE_ACTION_GET_VALUE</a><br>
<a href="doc012.html#i94">SANE_ACTION_SET_AUTO</a><br>
<a href="doc012.html#i93">SANE_ACTION_SET_VALUE</a><br>
<a href="doc012.html#i81">SANE_Authorization_Callback</a><br>
<a href="doc011.html#i16">SANE_Bool</a><br>
<a href="doc011.html#i14">SANE_Byte</a><br>
<a href="doc016.html#i140">SANE_Byte</a><br>
<a href="doc012.html#i113">sane_cancel</a><br>
<a href="doc011.html#i70">SANE_CAP_ADVANCED</a><br>
<a href="doc011.html#i72">SANE_CAP_ALWAYS_SETTABLE</a><br>
<a href="doc011.html#i68">SANE_CAP_AUTOMATIC</a><br>
<a href="doc011.html#i67">SANE_CAP_EMULATED</a><br>
<a href="doc011.html#i65">SANE_CAP_HARD_SELECT</a><br>
<a href="doc011.html#i71">SANE_CAP_HIDDEN</a><br>
<a href="doc011.html#i69">SANE_CAP_INACTIVE</a><br>
<a href="doc011.html#i66">SANE_CAP_SOFT_DETECT</a><br>
<a href="doc011.html#i64">SANE_CAP_SOFT_SELECT</a><br>
<a href="doc011.html#i24">SANE_Char</a><br>
<a href="doc016.html#i142">SANE_Char</a><br>
<a href="doc012.html#i88">sane_close</a><br>
<a href="doc011.html#i74">SANE_CONSTRAINT_NONE</a><br>
<a href="doc011.html#i75">SANE_CONSTRAINT_RANGE</a><br>
<a href="doc011.html#i78">SANE_CONSTRAINT_STRING_LIST</a><br>
<a href="doc011.html#i73">SANE_Constraint_Type</a><br>
<a href="doc011.html#i77">SANE_CONSTRAINT_WORD_LIST</a><br>
<a href="doc012.html#i90">sane_control_option</a><br>
<a href="doc010.html#i11">SANE_CURRENT_MAJOR</a><br>
<a href="doc011.html#i42">SANE_Device</a><br>
<a href="doc012.html#i85">sane_exit</a><br>
<a href="doc011.html#i17">SANE_FALSE</a><br>
<a href="doc011.html#i22">SANE_FIX</a><br>
<a href="doc011.html#i20">SANE_Fixed</a><br>
<a href="doc011.html#i21">SANE_FIXED_SCALE_SHIFT</a><br>
<a href="doc012.html#i101">SANE_Frame</a><br>
<a href="doc008.html#i7">SANE_FRAME_BLUE</a><br>
<a href="doc012.html#i106">SANE_FRAME_BLUE</a><br>
<a href="doc008.html#i3">SANE_FRAME_GRAY</a><br>
<a href="doc012.html#i102">SANE_FRAME_GRAY</a><br>
<a href="doc008.html#i6">SANE_FRAME_GREEN</a><br>
<a href="doc012.html#i105">SANE_FRAME_GREEN</a><br>
<a href="doc008.html#i2">SANE_FRAME_MIME</a><br>
<a href="doc008.html#i10">SANE_FRAME_MIME</a><br>
<a href="doc012.html#i109">SANE_FRAME_MIME</a><br>
<a href="doc008.html#i1">SANE_FRAME_RAW</a><br>
<a href="doc008.html#i8">SANE_FRAME_RAW</a><br>
<a href="doc008.html#i9">SANE_FRAME_RAW</a><br>
<a href="doc012.html#i107">SANE_FRAME_RAW</a><br>
<a href="doc012.html#i108">SANE_FRAME_RAW</a><br>
<a href="doc008.html#i5">SANE_FRAME_RED</a><br>
<a href="doc012.html#i104">SANE_FRAME_RED</a><br>
<a href="doc008.html#i4">SANE_FRAME_RGB</a><br>
<a href="doc012.html#i103">SANE_FRAME_RGB</a><br>
<a href="doc012.html#i86">sane_get_devices</a><br>
<a href="doc012.html#i89">sane_get_option_descriptor</a><br>
<a href="doc012.html#i99">sane_get_parameters</a><br>
<a href="doc012.html#i115">sane_get_select_fd</a><br>
<a href="doc011.html#i28">SANE_Handle</a><br>
<a href="doc016.html#i144">SANE_Handle</a><br>
<a href="doc012.html#i95">SANE_INFO_INEXACT</a><br>
<a href="doc012.html#i98">SANE_INFO_INVALIDATE_PREVIEW</a><br>
<a href="doc012.html#i96">SANE_INFO_RELOAD_OPTIONS</a><br>
<a href="doc012.html#i111">SANE_INFO_RELOAD_OPTIONS</a><br>
<a href="doc012.html#i97">SANE_INFO_RELOAD_PARAMS</a><br>
<a href="doc012.html#i80">sane_init</a><br>
<a href="doc011.html#i19">SANE_Int</a><br>
<a href="doc017.html#i169">SANE_NET_AUTHORIZE</a><br>
<a href="doc017.html#i170">SANE_NET_AUTHORIZE</a><br>
<a href="doc017.html#i167">SANE_NET_CANCEL</a><br>
<a href="doc017.html#i168">SANE_NET_CANCEL</a><br>
<a href="doc017.html#i156">SANE_NET_CLOSE</a><br>
<a href="doc017.html#i157">SANE_NET_CLOSE</a><br>
<a href="doc017.html#i161">SANE_NET_CONTROL_OPTION</a><br>
<a href="doc017.html#i162">SANE_NET_CONTROL_OPTION</a><br>
<a href="doc017.html#i172">SANE_NET_EXIT</a><br>
<a href="doc017.html#i173">SANE_NET_EXIT</a><br>
<a href="doc017.html#i152">SANE_NET_GET_DEVICES</a><br>
<a href="doc017.html#i153">SANE_NET_GET_DEVICES</a><br>
<a href="doc017.html#i158">SANE_NET_GET_OPTION_DESCRIPTORS</a><br>
<a href="doc017.html#i159">SANE_NET_GET_OPTION_DESCRIPTORS</a><br>
<a href="doc017.html#i163">SANE_NET_GET_PARAMETERS</a><br>
<a href="doc017.html#i164">SANE_NET_GET_PARAMETERS</a><br>
<a href="doc017.html#i150">SANE_NET_INIT</a><br>
<a href="doc017.html#i151">SANE_NET_INIT</a><br>
<a href="doc017.html#i154">SANE_NET_OPEN</a><br>
<a href="doc017.html#i155">SANE_NET_OPEN</a><br>
<a href="doc017.html#i165">SANE_NET_START</a><br>
<a href="doc017.html#i166">SANE_NET_START</a><br>
<a href="doc012.html#i87">sane_open</a><br>
<a href="doc011.html#i46">SANE_Option_Descriptor</a><br>
<a href="doc011.html#i62">SANE_OPTION_IS_ACTIVE</a><br>
<a href="doc011.html#i63">SANE_OPTION_IS_SETTABLE</a><br>
<a href="doc012.html#i100">SANE_Parameters</a><br>
<a href="doc011.html#i76">SANE_Range</a><br>
<a href="doc012.html#i112">sane_read</a><br>
<a href="doc012.html#i114">sane_set_io_mode</a><br>
<a href="doc012.html#i110">sane_start</a><br>
<a href="doc011.html#i29">SANE_Status</a><br>
<a href="doc011.html#i41">SANE_STATUS_ACCESS_DENIED</a><br>
<a href="doc011.html#i32">SANE_STATUS_CANCELLED</a><br>
<a href="doc011.html#i38">SANE_STATUS_COVER_OPEN</a><br>
<a href="doc011.html#i33">SANE_STATUS_DEVICE_BUSY</a><br>
<a href="doc011.html#i35">SANE_STATUS_EOF</a><br>
<a href="doc011.html#i30">SANE_STATUS_GOOD</a><br>
<a href="doc012.html#i79">SANE_STATUS_GOOD</a><br>
<a href="doc011.html#i34">SANE_STATUS_INVAL</a><br>
<a href="doc011.html#i39">SANE_STATUS_IO_ERROR</a><br>
<a href="doc011.html#i36">SANE_STATUS_JAMMED</a><br>
<a href="doc011.html#i37">SANE_STATUS_NO_DOCS</a><br>
<a href="doc011.html#i40">SANE_STATUS_NO_MEM</a><br>
<a href="doc011.html#i31">SANE_STATUS_UNSUPPORTED</a><br>
<a href="doc011.html#i25">SANE_String</a><br>
<a href="doc016.html#i143">SANE_String</a><br>
<a href="doc011.html#i27">SANE_String_Const</a><br>
<a href="doc012.html#i116">sane_strstatus</a><br>
<a href="doc011.html#i18">SANE_TRUE</a><br>
<a href="doc011.html#i48">SANE_TYPE_BOOL</a><br>
<a href="doc011.html#i52">SANE_TYPE_BUTTON</a><br>
<a href="doc011.html#i50">SANE_TYPE_FIXED</a><br>
<a href="doc011.html#i53">SANE_TYPE_GROUP</a><br>
<a href="doc011.html#i49">SANE_TYPE_INT</a><br>
<a href="doc011.html#i51">SANE_TYPE_STRING</a><br>
<a href="doc011.html#i54">SANE_Unit</a><br>
<a href="doc011.html#i23">SANE_UNFIX</a><br>
<a href="doc011.html#i57">SANE_UNIT_BIT</a><br>
<a href="doc011.html#i59">SANE_UNIT_DPI</a><br>
<a href="doc011.html#i61">SANE_UNIT_MICROSECOND</a><br>
<a href="doc011.html#i58">SANE_UNIT_MM</a><br>
<a href="doc011.html#i55">SANE_UNIT_NONE</a><br>
<a href="doc011.html#i60">SANE_UNIT_PERCENT</a><br>
<a href="doc011.html#i56">SANE_UNIT_PIXEL</a><br>
<a href="doc011.html#i47">SANE_Value_Type</a><br>
<a href="doc010.html#i12">SANE_VERSION_CODE</a><br>
<a href="doc010.html#i13">SANE_VERSION_MAJOR</a><br>
<a href="doc011.html#i15">SANE_Word</a><br>
<a href="doc016.html#i141">SANE_Word</a><br>
<a href="doc014.html#i123">scan area options</a><br>
<a href="doc014.html#i120">scan resolution</a><br>
<a href="doc014.html#i138">scanner button options</a><br>
<a href="doc014.html#i134">shadow options</a><br>
<a href="doc014.html#i130">source options</a><br>
<a href="doc016.html#i148">structure</a><br>
<p><a href="doc014.html#i131">threshold option</a><br>
<a href="doc014.html#i124">tl-x</a><br>
<a href="doc014.html#i125">tl-y</a><br>
<a href="doc011.html#i45">Type Strings</a><br>
<p><a href="doc016.html#i149">union</a><br>
<a href="doc012.html#i83">username</a><br>
<p><a href="doc011.html#i44">Vendor Strings</a><br>
<p><a href="doc014.html#i118">well-known options</a><br>
</multicol><p><hr>
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<title>Footnotes</title><h1>Footnotes</h1><p>
<hr><p><b><a href="doc011.html#F1">1</a></b> This is different from ANSI C where
any non-zero integer value represents logical TRUE.
<hr><p><b><a href="doc017.html#F2">2</a></b> The sane network
daemon should be careful not to leak information in the undefined
portion of the reply.

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<title>./sane</title>
<p>
<p>
<p>
<p>
<p>
<p>
<p>
<p><center><h1><font size=+4>SANE Standard Version 2.0 proposal 0.08 - rauch/beck</font></h1></center>
<center></center>
<center>Dec 8, 2002</center>
<p>
<p><h1><a href="doc002.html">1 Preface</a></h1><h1><a href="doc004.html">2 Introduction</a></h1><h1><a href="doc006.html">3 The SANE Environment</a></h1><h1><a href="doc009.html">4 The SANE Application Programmer Interface (API)</a></h1><h1><a href="doc015.html">5 Network Protocol</a></h1><h1><a href="doc018.html">6 Contact Information</a></h1><p><hr>
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@ -2,69 +2,35 @@
<html>
<head>
<title>SANE - Standard Version 2</title>
<title>SANE - Standard Version 2 Draft</title>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
<meta name="author" content="Henning Meier-Geinitz">
<meta name="keywords" content="sane, standard, 2, sane2, documentation">
<meta name="description" content="Development of the SANE2 standard">
<link href="mailto:hmg-guest@users.alioth.debian.org" rev="made">
<link href="../favicon.ico" type="image/x-icon" rel="icon">
<link href="../favicon.ico" type="image/x-icon" rel="icon">
<link href="../favicon.ico" type="image/x-icon" rel="shortcut icon">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<body bgcolor="#FFFFFF" text="#000000">
<center>
<a href="../" target="_top"><img
src="../images/sane.png" alt="SANE" height="117" width="346" border="0"></a>
</center>
src="../images/sane.png" alt="SANE" height="117" width="346" border="0"></a>
</center>
<center>
<h1>SANE - Standard Version 2</h1>
<h1>SANE - Standard Version 2 Draft</h1>
</center>
<p>
The SANE standard version 2 is currently under development. It shouldn't be
used yet for production software because some important parts are still
missing. Most of the work to update the standard has been done by
Andreas Beck and Oliver Rauch. The discussion takes place on the <a
href="../mailing-lists.html">sane-standard mailing list</a>. The standard is
in CVS, see <a href="../cvs.html">CVS page</a>. The SANE2 standard is in
branch DEVEL_2_0_BRANCH-1. Use the following command to get this branch:
The SANE Standard has been reformatted and moved to
<a href="https://sane-project.gitlab.io/standard/">https://sane-project.gitlab.io/standard/</a>.
You can find the latest revision of the Version 2 <em>draft</em>
there as well.
</p>
<pre>
export CVS_RSH=ssh
cvs -z3 -d:ext:developername@cvs.alioth.debian.org:/cvsroot/sane co -d sane2 -r DEVEL_2_0_BRANCH-1 sane-backends
</pre>
<p>
There is a <a href="sane2-todo.html">TODO list</a> and some snapshots of
the standard are available in several formats:
</p>
<ul>
<li>
<a href="0.08/">SANE2 standard draft 0.08 as HTML</a> (or <a
href="0.08/sane2-0.08.tex">tex</a>, <a
href="0.08/sane2-0.08.dvi">dvi</a>, <a href="0.08/sane2-0.08.ps">ps</a>)
</li>
<li>
<a href="0.07/">SANE2 standard draft 0.07 as HTML</a> (or <a
href="0.07/sane2-0.07.tex">tex</a>, <a
href="0.07/sane2-0.07.dvi">dvi</a>, <a href="0.07/sane2-0.07.ps">ps</a>)
</li>
<li>
SANE2 standard draft 0.06 as <a href="0.06/sane2-0.06.tex.gz">tex</a>,
<a href="0.06/sane2-0.06.dvi.gz">dvi</a>, <a
href="0.06/sane2-0.06.ps.gz">ps</a>
</li>
<li>
SANE2 standard draft 0.05 as <a href="0.05/sane2-0.05.tex.gz">tex</a>,
<a href="0.05/sane2-0.05.dvi.gz">dvi</a>, <a
href="0.05/sane2-0.05.ps.gz">ps</a>
</li>
</ul>
Please note that this page is slated for removal. Update your
references as necessary.
<hr>
<p>