Re: Gamma and xsane

Andreas Dilger (adilger@enel.ucalgary.ca)
Sat, 22 May 1999 15:37:42 -0600 (MDT)

Oliver writes:
> If you have a 8/24 bit scanner you reduce the number of used colors.
> On 30 or 36 bit scanners you can use small gamma value changes (0.x-1.y)
> without loosing any or much used colors.

If you subsequently convert the 30/36 bit color images to 24-bit color, you
shouldn't have any loss of color resolution.

> That works with linux too, but if you want that your image looks ok on other
> systems, you have to correct the colors that they look ok without any further
> corrections! If you use gamma=1.0 the images are all too dark!

If you use PNG format images, and if xsane writes a gAMA chunk (it should!),
then you won't have any such problems. This is one of reasons why PNG is
becoming more popular. Also, there are other features that PNG has that
xsane should take advantage of - like pHYs to record the original pixel
size characteristics (dpi), sBIT to record the original bit depth, tIME to
hold the image scanning time, tEXt to hold Software and Source comments...
Info that xsane already has and you might need in the future when working
with the image.

Cheers, Andreas

-- 
Andreas Dilger  University of Calgary \ "If a man ate a pound of pasta and
                Micronet Research Group \ a pound of antipasto, would they
Dept of Electrical & Computer Engineering \  cancel out, leaving him still
http://www-mddsp.enel.ucalgary.ca/People/adilger/      hungry?" -- Dogbert



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