> Hi all,
>
> I wonder if wouldn't be useful to incorporate some 'level adjustment
> widget' under xscanimage, as a complement to the custom gamma correction.
> It should work very much the same very as level adjustment works under
> the gimp (and probably each other image manipulation program), i.e. you
> tell the program that you want the intensity range from current intensity,
> say, 20 to 230 mapped to the full range of 0 to 255, because in your image
> there are almost no very dark and very bright regions in the range from 0 to
> 19 and 231 to 255. Doing this while scanning should have the adavantage
> that at least some (if not all) scanners have the ability to adjust
> their absolute white and black level, so that you get always the full
> range of 256 intensity shades, whereas if you adjust levels afterwards,
> you lose always some shades, which sometimes makes a visible difference.
>
> Such widget should even look very much the same as the level adjustment
> widget under the gimp, i.e. you should see a histogram of the current
> scan region (possibly evaluated by the preview) and you should be able
> to set you new black and white levels (and perhaps the 'gamma point')
> from the histogram; then the scanner gets recalibrated to the new
> black and white points, and voila, you new scan is done with the new tonal
> range.
>
> Some scanner software for windows has this - in my opinion very useful,
> probably more useful than custom gamma correction curves - feature. Is there
> some thought of implementing something like that for xscanimage?
Hi Steffen,
I think this a a very good idea.
But we should discuss how the highligh and shadow functions that are supported
by some scanners are included and how it is done if you only have a gamma
function.
The scanners that have a 30 to 24 bits or 36 to 24 bits gamma table will get
better
results if you send a gamma table to the scanner that does include the
intensity-range.
And to make it much more difficult: there are some scanners that have a digital
gamma
table and an analog amma function. The analog gamma function does not reduce the
number of used colors, so it should be prefered if available.
And to make it very good, it would be great if you would see a change online in
the
preview-window, without a new scan.
So it is not very simple.
Bye
Oliver
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