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78 wiersze
3.9 KiB
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<!-- received="Mon May 11 21:40:44 1998 PDT" -->
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<!-- sent="Mon, 11 May 1998 21:40:43 -0700" -->
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<!-- name="David Mosberger-Tang" -->
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<!-- email="David.Mosberger@acm.org" -->
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<!-- subject="Re: problems with snapscan and scanimage" -->
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<!-- id="199805120440.VAA15693@panda.mostang.com" -->
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<!-- inreplyto="19980512034234Z13333-19035+343@scapa.cs.ualberta.ca" -->
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<title>sane-devel: Re: problems with snapscan and scanimage</title>
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<h1>Re: problems with snapscan and scanimage</h1>
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<b>David Mosberger-Tang</b> (<a href="mailto:David.Mosberger@acm.org"><i>David.Mosberger@acm.org</i></a>)<br>
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<i>Mon, 11 May 1998 21:40:43 -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#130">[ date ]</a><a href="index.html#130">[ thread ]</a><a href="subject.html#130">[ subject ]</a><a href="author.html#130">[ author ]</a>
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<li> <b>Next message:</b> <a href="0131.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<li> <b>Previous message:</b> <a href="0129.html">Pkirchg: "Re: HP Photoscan"</a>
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<li> <b>In reply to:</b> <a href="0127.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<li> <b>Next in thread:</b> <a href="0131.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<li> <b>Reply:</b> <a href="0131.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<li> <b>Reply:</b> <a href="0133.html">Rogier Wolff: "Re: problems with snapscan and scanimage"</a>
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</ul>
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<i>>>>>> On Mon, 11 May 1998 21:42:28 -0600 (MDT), <a href="mailto:charter@cs.ualberta.ca">charter@cs.ualberta.ca</a> said:</i><br>
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<p>
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<i> >> (*) After a closer look I'd say it does not produce 10 bits -- it</i><br>
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<i> >> just *claims* to :-)</i><br>
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<p>
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Kevin> The output from the scanner to the host is 8 bits per<br>
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Kevin> sample, but the scanner allows the host to download a<br>
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Kevin> 10-bit gamma table for each channel. Presumably this gives<br>
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Kevin> finer control over gamma correction (or "tone curving")<br>
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Kevin> than the 8-bit tables, despite the fact that the data is<br>
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Kevin> being converted to 8 bits before it's sent to the host.<br>
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<p>
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A couple of notes:<br>
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<p>
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- The SANE API supports depths of 1 bit/channel or any<br>
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positive integer multiple of 8. 10 bits/channel is _not_<br>
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a supported depth.<br>
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<p>
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- Most (all?) current frontends are limited to 8 bits/channel.<br>
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This isn't hard to fix, it's just no fun to do without<br>
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hardware to test it with.<br>
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<p>
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- A 10-bit gamma table does indeed make sense even when the<br>
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output is only 8 bits/channel. Fortunately, this can be<br>
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supported just fine with SANE (e.g., simply allow values in<br>
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the range 0..1023 for the gamma vector elements).<br>
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<p>
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I applied a patch similar to Mikko's to the SnapScan backend---hope<br>
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that's all right.<br>
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<p>
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Thanks,<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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Source code, list archive, and docs: <a href="http://www.mostang.com/sane/">http://www.mostang.com/sane/</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="0131.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<li> <b>Previous message:</b> <a href="0129.html">Pkirchg: "Re: HP Photoscan"</a>
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<li> <b>In reply to:</b> <a href="0127.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<!-- nextthread="start" -->
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<li> <b>Next in thread:</b> <a href="0131.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<li> <b>Reply:</b> <a href="0131.html">charter@cs.ualberta.ca: "Re: problems with snapscan and scanimage"</a>
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<li> <b>Reply:</b> <a href="0133.html">Rogier Wolff: "Re: problems with snapscan and scanimage"</a>
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<!-- reply="end" -->
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</ul>
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