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<!-- received="Sat Aug 14 19:49:54 1999 PDT" -->
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<!-- sent="Sun, 15 Aug 1999 03:49:16 +0100 (GMT)" -->
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<!-- name="Nick Lamb" -->
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<!-- email="njl98r@ecs.soton.ac.uk" -->
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<!-- subject="Re: Starting a discussion about SANE and TWAIN..." -->
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<!-- inreplyto="199908150215.TAA03217@icarus.com" -->
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<title>sane-devel: Re: Starting a discussion about SANE and TWAIN...</title>
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<h1>Re: Starting a discussion about SANE and TWAIN...</h1>
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<b>Nick Lamb</b> (<a href="mailto:njl98r@ecs.soton.ac.uk"><i>njl98r@ecs.soton.ac.uk</i></a>)<br>
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<i>Sun, 15 Aug 1999 03:49:16 +0100 (GMT)</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#156">[ date ]</a><a href="index.html#156">[ thread ]</a><a href="subject.html#156">[ subject ]</a><a href="author.html#156">[ author ]</a>
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<li> <b>Next message:</b> <a href="0157.html">Stephen Williams: "Re: Starting a discussion about SANE and TWAIN..."</a>
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<li> <b>Previous message:</b> <a href="0155.html">Nick Lamb: "Re: SANE V2"</a>
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<li> <b>In reply to:</b> <a href="0154.html">Stephen Williams: "Re: Starting a discussion about SANE and TWAIN..."</a>
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</ul>
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<!-- body="start" -->
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On Sat, 14 Aug 1999, Stephen Williams wrote:<br>
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<p>
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<i>> So all I'm looking for at the moment is some sort of means to negotiate</i><br>
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<i>> frame formats.</i><br>
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<p>
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Ok. IIRC Your scanners can do RGB, but prefer not to for speed reasons?<br>
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So in writing the backend, first start by supporting this (slow) option<br>
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as the default and then add an option (eventually to be a well-known<br>
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option in SANE 2.0) which controls the compression.<br>
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<p>
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I haven't finished looking at this, but so far I think this will work<br>
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for SANE_FRAME_JFIF (perhaps code 6 in the enumeration)<br>
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<p>
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OPTION ONE -- If the backend knows before sending any data how much<br>
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there will be exactly in the JFIF image.<br>
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<p>
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format = SANE_FRAME_JFIF (6)<br>
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last_frame = TRUE<br>
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lines = 1<br>
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depth = 8<br>
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pixels_per_line = 0<br>
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bytes_per_line = sizeof(JFIF image)<br>
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<p>
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OPTION TWO -- If the backend doesn't know how much data there is until<br>
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later, or until it runs out.<br>
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<p>
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format = SANE_FRAME_JFIF (6)<br>
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last_frame = TRUE<br>
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lines = -1<br>
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depth = 8<br>
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pixels_per_line = 0<br>
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bytes_per_line = 4096 (or 65536, whatever)<br>
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<p>
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A compliant SANE 1.0 frontend will reject such frames without danger, a<br>
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proposed 2.0 frontend without any JFIF code will save them to a file<br>
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and likely use a buffer with size ~= bytes_per_line.<br>
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An intelligent SANE 2.0 frontend will know to sane_read(...) until EOF<br>
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and then deal with the JFIF data appropriately.<br>
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<p>
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OPTION TWO is probably the one to go for, but I like OPTION ONE at lot<br>
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because it's so very simple ;)<br>
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<p>
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Might try to write a modifed scanimage which handles all this tomorrow<br>
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if I get a chance. Now, time for bed.<br>
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<p>
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Nick.<br>
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<p>
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<p>
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<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">majordomo@mostang.com</a>
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</pre>
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<!-- body="end" -->
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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="0157.html">Stephen Williams: "Re: Starting a discussion about SANE and TWAIN..."</a>
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<li> <b>Previous message:</b> <a href="0155.html">Nick Lamb: "Re: SANE V2"</a>
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<li> <b>In reply to:</b> <a href="0154.html">Stephen Williams: "Re: Starting a discussion about SANE and TWAIN..."</a>
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<!-- nextthread="start" -->
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</ul>
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