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<TITLE>sane-devel: Re: image data format polarity</TITLE>
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<META NAME="Author" CONTENT="Ingo Wilken (Ingo.Wilken@Informatik.Uni-Oldenburg.DE)">
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<META NAME="Subject" CONTENT="Re: image data format polarity">
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<H1>Re: image data format polarity</H1>
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<STRONG>From:</STRONG> Ingo Wilken (<A HREF="mailto:Ingo.Wilken@Informatik.Uni-Oldenburg.DE?Subject=Re:%20image%20data%20format%20polarity&In-Reply-To=<E13YO9H-0007Qb-00@petersfehn.Informatik.Uni-Oldenburg.DE>"><EM>Ingo.Wilken@Informatik.Uni-Oldenburg.DE</EM></A>)<BR>
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<STRONG>Date:</STRONG> Mon Sep 11 2000 - 00:37:03 PDT
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<LI><STRONG>Next message:</STRONG> <A HREF="0097.html">Nick Lamb: "Re: image data format polarity"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0095.html">Peck Dickens: "Re: SnapScan Backend"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0093.html">Petter Reinholdtsen: "Re: image data format polarity"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0097.html">Nick Lamb: "Re: image data format polarity"</A>
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<EM>> [David Paschal]
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</EM><BR>
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<EM>> > On the other hand, for 1-bit depths (lineart, halftone), 0 means
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</EM><BR>
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<EM>> > white and 1 means black. Is there any particular reason for this,
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</EM><BR>
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<EM>> > especially since xsane and xscanimage both end up having to invert
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</EM><BR>
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<EM>> > it anyway in order to display a preview?
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</EM><BR>
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<EM>> This sounds like a bug to me. The only partly sensible reason I can
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</EM><BR>
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<EM>> make up on the fly to use a encoding like this is to make sure black
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</EM><BR>
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<EM>> writing on white paper give mostly 0 bits.
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</EM><BR>
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<P>That's not a bug, it's the PBM image format, see pbm(5):
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<BR>
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<P># It was originally designed to make it reasonable to mail
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<BR>
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# bitmaps between different types of machines using the typical stupid
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<BR>
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# network mailers we have today.
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<BR>
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[...]
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<BR>
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# - Width * height bits, each either '1' or '0', starting at the top-left
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<BR>
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# corner of the bitmap, proceeding in normal English reading order.
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<BR>
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#
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<BR>
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# - The character '1' means black, '0' means white.
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<BR>
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<P>And yes, it obviously was designed that way, so a human can see the
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<BR>
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image without using a graphics display program, just by looking at
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<BR>
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the ASCII representation (assuming a large screen and proper formatting,
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<BR>
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the manpage has a tiny example).
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<BR>
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<P>Regards,
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<BR>
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Ingo
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<BR>
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<P><PRE>
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--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20image%20data%20format%20polarity&In-Reply-To=<E13YO9H-0007Qb-00@petersfehn.Informatik.Uni-Oldenburg.DE>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0097.html">Nick Lamb: "Re: image data format polarity"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0095.html">Peck Dickens: "Re: SnapScan Backend"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0093.html">Petter Reinholdtsen: "Re: image data format polarity"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0097.html">Nick Lamb: "Re: image data format polarity"</A>
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<EM>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Mon Sep 11 2000 - 00:32:35 PDT</EM>
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