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<!-- received="Mon May 26 10:20:54 1997 MST" -->
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<!-- sent="Mon, 26 May 1997 09:43:57 -0700" -->
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<!-- name="David Mosberger-Tang" -->
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<!-- email="davidm@azstarnet.com" -->
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<!-- subject="Re: a priori image dimensions" -->
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<!-- id="199705261643.JAA15681@panda.mosberger" -->
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<!-- inreplyto="86g1vap7a2.fsf@localhost.profitpress.com" -->
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<title>sane-devel: Re: a priori image dimensions</title>
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<h1>Re: a priori image dimensions</h1>
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<b>David Mosberger-Tang</b> (<a href="mailto:davidm@azstarnet.com"><i>davidm@azstarnet.com</i></a>)<br>
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<i>Mon, 26 May 1997 09:43:57 -0700</i>
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<p>
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<ul>
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<li> <b>Messages sorted by:</b> <a href="date.html#19">[ date ]</a><a href="index.html#19">[ thread ]</a><a href="subject.html#19">[ subject ]</a><a href="author.html#19">[ author ]</a>
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<li> <b>Next message:</b> <a href="0020.html">becka@sunserver1.rz.uni-duesseldorf.de: "Re: a priori image dimensions"</a>
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<li> <b>Previous message:</b> <a href="0018.html">Gordon Matzigkeit: "a priori image dimensions"</a>
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<i>>>>>> On 26 May 1997 09:44:37 -0600, Gordon Matzigkeit <<a href="mailto:gord@m-tech.ab.ca">gord@m-tech.ab.ca</a>> said:</i><br>
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<p>
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Gord> Hi! Here's question for the list before I spend the time to<br>
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Gord> download sane-0.57...<br>
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<p>
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Gord> A problem that I've discovered in my PINT backend is that the<br>
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Gord> dimensions (both X and Y) cannot be known until the scan is<br>
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Gord> started. I've noticed the following line in the TODO:<br>
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<p>
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That is correct. But x can be known before the first chunk of data is<br>
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read. The specs allow only y to be unknown once a scan has started<br>
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(primarily to accommodate hand-scanners).<br>
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<p>
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Gord> - xscan: scanning of images whose heights is not known a<br>
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Gord> priori is not supported yet; this is going to be important for<br>
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Gord> handheld scanners<br>
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<p>
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Gord> Does anybody have ideas on how to implement this, and/or has<br>
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Gord> it been done in 0.57?<br>
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<p>
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The code in preview.c handles this properly, but the actual scan<br>
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engine in xscanimage.c doesn't. In standalone mode, we could use code<br>
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similar to the one in scanimage.c whereas in GIMP mode we would have<br>
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to increase the image size as scanning progresses.<br>
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<p>
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Gord> The easiest way I can think of is to have a call to<br>
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Gord> sane_get_parameters after the scan has completed to find out<br>
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Gord> what actually happened.<br>
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<p>
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The problem is that sane_get_parameters() will return a height of -1<br>
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for hand-scanners, so you do have to read all the data to find how<br>
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tall the image is.<br>
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<p>
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Gord> Maybe space for the PNM header could be reserved before the<br>
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Gord> raw data is written, such as:<br>
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<p>
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That sounds like a reasonable strategy as it would maintain the<br>
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property that xscanimage never buffers an entire image itself.<br>
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<p>
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--david<br>
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<p>
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<pre>
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--
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</pre>
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<p>
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<ul>
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<!-- next="start" -->
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<li> <b>Next message:</b> <a href="0020.html">becka@sunserver1.rz.uni-duesseldorf.de: "Re: a priori image dimensions"</a>
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<li> <b>Previous message:</b> <a href="0018.html">Gordon Matzigkeit: "a priori image dimensions"</a>
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