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<!-- received="Thu Dec 4 10:30:01 1997 PST" -->
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<!-- sent="Thu, 04 Dec 1997 19:31:56 +0100" -->
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<!-- name="Nicolas Lucas de Peslouan" -->
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<!-- email="nlp@usa.net" -->
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<!-- subject="Using preview mode to scan in color with UMAX Astra 600/610S." -->
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<title>sane-devel: Using preview mode to scan in color with UMAX Astra 600/610S.</title>
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<h1>Using preview mode to scan in color with UMAX Astra 600/610S.</h1>
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<b>Nicolas Lucas de Peslouan</b> (<a href="mailto:nlp@usa.net"><i>nlp@usa.net</i></a>)<br>
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<i>Thu, 04 Dec 1997 19:31:56 +0100</i>
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<p>
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<li> <b>Next message:</b> <a href="0024.html">Joachim Woll: "xerox"</a>
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Hi !<br>
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<p>
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I've done some more tests with the output from the Umax Astra 610S in<br>
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preview-color mode. (sane-0.68)<br>
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<p>
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I worked with a "preview-umax:" file left by xscanimage after a color<br>
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preview. (I assume this is close enought to the true output from the<br>
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scanner to trust - at least - the bytes order). This of course also work<br>
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with the output of "scanimage --preview=yes".<br>
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<p>
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The scanned image is a white paper, with 3 square: RED, GREEN and BLUE,<br>
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in order to find RGB signals.<br>
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<p>
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The initial file show a three-column image, each column having the value<br>
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for one of the R, G of B signal level.<br>
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<p>
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I first tried to swap bytes (R1R2R3R4...G1G2G3G4...B1B2B3B4... to<br>
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R1G1B1R2G2B2R3G3B3R4G4B4...).<br>
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<p>
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This gave a one-column image, but having part of the right side shown on<br>
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the left. (ABCD -> DABC), and some strang color change.<br>
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<p>
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I then tried the same swap process but removing some noise at the top.<br>
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(about 185 bytes).<br>
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<p>
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This work, showing a properly formated picture (ABCD) but having the<br>
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wrong colors. (red shown as blue, green shown as red and blue shown as<br>
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green).<br>
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<p>
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I then tried to remove more bytes, keeping the value "~185 in mind. The<br>
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correct noise length seems to be LengthOfLineInPixel*2+~185.<br>
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<p>
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With this, we can have some sort of preview image.<br>
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<p>
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But the image also shown some noise at the end, and some missing upper<br>
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margin at the top.<br>
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<p>
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I tried to scan a white paper, and find that the noise at the begining<br>
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have the same values as the whole image. (form ~240 to 255). I then scan<br>
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a black paper, and find that the noise at the begining have again the<br>
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same values as the whole image (form 0 to ~32). In short, the "noise" in<br>
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not noise, but trailing bytes from a previous line. <br>
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<p>
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At this point, we have to way to go :<br>
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<p>
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- The scanner does not return the first few lines of the image, and we<br>
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need to request the image in another way.<br>
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- The scanner do return the first few lines, but they are lost/dropped<br>
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somewhere.<br>
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<p>
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For now, we are able to convert some "preview-mode" image to something<br>
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readable, but with poor quality. (By the way, does anyone know the real<br>
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resolution used to do a preview ?)<br>
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<p>
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If someone want to have a look at the quick-and-dirty C program to<br>
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convert from bad to better, just ask. It probably needs to be rewritten<br>
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to enhance performances, but...<br>
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<p>
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Nicolas.<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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<li> <b>Next message:</b> <a href="0024.html">Joachim Woll: "xerox"</a>
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<li> <b>Previous message:</b> <a href="0022.html">Michael K. Johnson: "Re: new-sane-homepage-outfit"</a>
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