sane-project-website/old-archive/1998-08/0013.html

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<!-- name="Steffen Renisch" -->
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<!-- subject="level adjustment widget in xscanimage?" -->
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<title>sane-devel: level adjustment widget in xscanimage?</title>
<h1>level adjustment widget in xscanimage?</h1>
<b>Steffen Renisch</b> (<a href="mailto:steffen@thutmosis.rz-berlin.mpg.de"><i>steffen@thutmosis.rz-berlin.mpg.de</i></a>)<br>
<i>Wed, 5 Aug 1998 12:57:58 +0200 (CEST)</i>
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Hi all,<br>
<p>
I wonder if wouldn't be useful to incorporate some 'level adjustment<br>
widget' under xscanimage, as a complement to the custom gamma correction.<br>
It should work very much the same very as level adjustment works under<br>
the gimp (and probably each other image manipulation program), i.e. you <br>
tell the program that you want the intensity range from current intensity,<br>
say, 20 to 230 mapped to the full range of 0 to 255, because in your image<br>
there are almost no very dark and very bright regions in the range from 0 to<br>
19 and 231 to 255. Doing this while scanning should have the adavantage<br>
that at least some (if not all) scanners have the ability to adjust<br>
their absolute white and black level, so that you get always the full<br>
range of 256 intensity shades, whereas if you adjust levels afterwards,<br>
you lose always some shades, which sometimes makes a visible difference.<br>
<p>
Such widget should even look very much the same as the level adjustment<br>
widget under the gimp, i.e. you should see a histogram of the current<br>
scan region (possibly evaluated by the preview) and you should be able<br>
to set you new black and white levels (and perhaps the 'gamma point')<br>
from the histogram; then the scanner gets recalibrated to the new <br>
black and white points, and voila, you new scan is done with the new tonal<br>
range.<br>
<p>
Some scanner software for windows has this - in my opinion very useful,<br>
probably more useful than custom gamma correction curves - feature. Is there <br>
some thought of implementing something like that for xscanimage?<br>
<p>
Steffen<br>
<a href="mailto:renisch@fhi-berlin.mpg.de">renisch@fhi-berlin.mpg.de</a><br>
<p>
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<li> <b>Next in thread:</b> <a href="0015.html">Matto Marjanovic: "Re: level adjustment widget in xscanimage?"</a>
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<li> <b>Reply:</b> <a href="0017.html">Oliver Rauch: "Re: level adjustment widget in xscanimage?"</a>
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