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102 wiersze
3.6 KiB
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<!-- received="Thu Sep 4 12:27:43 1997 MST" -->
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<!-- sent="Thu, 4 Sep 1997 20:19:23 +0200 (MET DST)" -->
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<!-- name="Oliver.Rauch@Wolfsburg.DE" -->
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<!-- email="Oliver.Rauch@Wolfsburg.DE" -->
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<!-- subject="umax scan resolution" -->
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<!-- id="199709041819.UAA10336@Babylon5.wolfsburg.de" -->
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<!-- inreplyto="" -->
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<title>sane-devel: umax scan resolution</title>
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<h1>umax scan resolution</h1>
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<a href="mailto:Oliver.Rauch@Wolfsburg.DE"><i>Oliver.Rauch@Wolfsburg.DE</i></a><br>
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<i>Thu, 4 Sep 1997 20:19:23 +0200 (MET DST)</i>
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<p>
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<ul>
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<li> <b>Next message:</b> <a href="0135.html">rwsimmon@ee.utah.edu: "support of Solaris x86?"</a>
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</ul>
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<!-- body="start" -->
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Hello Umax-scanner owners!<br>
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<p>
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In the moment the umax-sane-backend only supports as<br>
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maximum resolution the value "optical resolution" that is<br>
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set by the scanner and in some cases is only the half<br>
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of the resolution the firmware of the scanner supports.<br>
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<p>
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The scan-width is given as a value related to a resolution<br>
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of 1200 dpi. It is calculated:<br>
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<p>
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phys_width = width_in_pixels * 1200 / resolution;<br>
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<p>
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that works fine from 1 to 600 dpi.<br>
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<p>
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If I use more than 600 dpi, the scanner calculates<br>
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another length in pixels as I used for calculation,<br>
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so the scanned image is "crunched". If there is a<br>
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difference, then the scanner calculated one pixel less<br>
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than I expect.<br>
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<p>
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So I tried different ways to change the calculation,<br>
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the first is:<br>
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<p>
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phys_width = ( width_in_pixels + 0.5) * 1200 / resolution;<br>
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<p>
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and the second:<br>
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<p>
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phys_width = width_in_pixels * 1200 / resolution + 0.5<br>
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<p>
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(tried with double and integer and ...)<br>
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<p>
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but that doesn't make the thing better. Then sometimes<br>
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the scanner usese the right length, sometimes one pixel more<br>
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or one pixel less than I expect.<br>
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<p>
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In the UMAX scsi-protocol is described, how the resolutions<br>
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are created:<br>
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<p>
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O = hardware-resolution<br>
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S = selected resolution<br>
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D = O - S<br>
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<p>
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n-th pixel = INT ( n *O/D ) pixel of hardware-resolution , n=0..D<br>
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<p>
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that seem to be the pixels that are thrown away.<br>
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<p>
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<p>
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I don't have the time to find out what value<br>
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for phys_width (related to 1200 dpi) I have to set<br>
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to get width_in_pixels pixels back.<br>
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<p>
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If anybody likes to use the resolutions > optical_res<br>
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or > 600 dpi, say me how I do calculate it and I will<br>
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include it.<br>
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<p>
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----------<br>
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<p>
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30 bit support (e.g. for umax-Astra 1200S) is half done!<br>
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So I think it will be included into sane-0.64. But I don't<br>
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know if xscanimage supports more than 24 bits per pixel!<br>
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<p>
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But at least 30 bit gamma correction will work!<br>
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<p>
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Bye<br>
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Oliver<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.azstarnet.com/~axplinux/sane/">http://www.azstarnet.com/~axplinux/sane/</a>
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</pre>
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<p>
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<li> <b>Next message:</b> <a href="0135.html">rwsimmon@ee.utah.edu: "support of Solaris x86?"</a>
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<li> <b>Previous message:</b> <a href="0133.html">jim barchuk: "pnmto???? 'bad magic number'"</a>
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