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<!-- received="Wed Aug 5 10:27:43 1998 PDT" -->
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<!-- sent="Wed, 05 Aug 1998 19:03:14 +0200" -->
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<!-- name="Oliver Rauch" -->
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<!-- email="oliver.rauch@Wolfsburg.DE" -->
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<!-- subject="Re: level adjustment widget in xscanimage?" -->
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<title>sane-devel: Re: level adjustment widget in xscanimage?</title>
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<h1>Re: level adjustment widget in xscanimage?</h1>
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<b>Oliver Rauch</b> (<a href="mailto:oliver.rauch@Wolfsburg.DE"><i>oliver.rauch@Wolfsburg.DE</i></a>)<br>
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<i>Wed, 05 Aug 1998 19:03:14 +0200</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#17">[ date ]</a><a href="index.html#17">[ thread ]</a><a href="subject.html#17">[ subject ]</a><a href="author.html#17">[ author ]</a>
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<li> <b>Next message:</b> <a href="0018.html">Andrea Novara: "Mustek ScanMagic 4800P"</a>
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<li> <b>Previous message:</b> <a href="0016.html">Yuri Dario: "Re: SANEI_THREAD proposal"</a>
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<li> <b>Maybe in reply to:</b> <a href="0013.html">Steffen Renisch: "level adjustment widget in xscanimage?"</a>
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</ul>
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Steffen Renisch wrote:<br>
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<p>
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<i>> Hi all,</i><br>
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<i>></i><br>
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<i>> I wonder if wouldn't be useful to incorporate some 'level adjustment</i><br>
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<i>> widget' under xscanimage, as a complement to the custom gamma correction.</i><br>
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<i>> It should work very much the same very as level adjustment works under</i><br>
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<i>> the gimp (and probably each other image manipulation program), i.e. you</i><br>
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<i>> tell the program that you want the intensity range from current intensity,</i><br>
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<i>> say, 20 to 230 mapped to the full range of 0 to 255, because in your image</i><br>
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<i>> there are almost no very dark and very bright regions in the range from 0 to</i><br>
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<i>> 19 and 231 to 255. Doing this while scanning should have the adavantage</i><br>
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<i>> that at least some (if not all) scanners have the ability to adjust</i><br>
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<i>> their absolute white and black level, so that you get always the full</i><br>
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<i>> range of 256 intensity shades, whereas if you adjust levels afterwards,</i><br>
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<i>> you lose always some shades, which sometimes makes a visible difference.</i><br>
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<i>></i><br>
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<i>> Such widget should even look very much the same as the level adjustment</i><br>
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<i>> widget under the gimp, i.e. you should see a histogram of the current</i><br>
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<i>> scan region (possibly evaluated by the preview) and you should be able</i><br>
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<i>> to set you new black and white levels (and perhaps the 'gamma point')</i><br>
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<i>> from the histogram; then the scanner gets recalibrated to the new</i><br>
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<i>> black and white points, and voila, you new scan is done with the new tonal</i><br>
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<i>> range.</i><br>
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<i>></i><br>
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<i>> Some scanner software for windows has this - in my opinion very useful,</i><br>
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<i>> probably more useful than custom gamma correction curves - feature. Is there</i><br>
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<i>> some thought of implementing something like that for xscanimage?</i><br>
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<p>
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Hi Steffen,<br>
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<p>
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I think this a a very good idea.<br>
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But we should discuss how the highligh and shadow functions that are supported<br>
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by some scanners are included and how it is done if you only have a gamma<br>
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function.<br>
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The scanners that have a 30 to 24 bits or 36 to 24 bits gamma table will get<br>
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better<br>
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results if you send a gamma table to the scanner that does include the<br>
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intensity-range.<br>
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And to make it much more difficult: there are some scanners that have a digital<br>
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gamma<br>
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table and an analog amma function. The analog gamma function does not reduce the<br>
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<p>
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number of used colors, so it should be prefered if available.<br>
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And to make it very good, it would be great if you would see a change online in<br>
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the<br>
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preview-window, without a new scan.<br>
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<p>
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So it is not very simple.<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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<p>
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<pre>
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--
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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="0018.html">Andrea Novara: "Mustek ScanMagic 4800P"</a>
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<li> <b>Previous message:</b> <a href="0016.html">Yuri Dario: "Re: SANEI_THREAD proposal"</a>
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<li> <b>Maybe in reply to:</b> <a href="0013.html">Steffen Renisch: "level adjustment widget in xscanimage?"</a>
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<!-- nextthread="start" -->
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<!-- reply="end" -->
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</ul>
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