[sane-devel] What exactly does scanning software do?

Ulrich Deiters ulrich.deiters at uni-koeln.de
Fri Nov 9 22:59:13 UTC 2007


what the scanner adjustments do depends very much on the scanner.
The selection of colour/grayscale/lineart affects the sampling
and scanning speed on practically all scanners. Adjustments
of brightness, contrast, colour hues are used to fine-tune the
signal amplifiers on many scanners, but there are some where
the adjustments are done by software after the scan.

If your scanner produces 3x8 bit RGB data only, you can expect
that it does its adjustments by hardware, for otherwise you
would lose too much quality (e.g., a too dim picture using
pixel values between 0 and 63 can be "lit up" by software
to use the full range, 0 to 255, but then you would still
have merely 64 shades of colour instead of 255). If your
scanner produces 3x12 or 3x16 bit RGB data, it is possible
that the signal amplifiers work with fixed settings, and
corrections are done by software.


Ulrich Deiters

Prof. Dr. Ulrich K. Deiters      ______________________________________
Institut f. Physikalische Chemie \ Luxemburger Str. 116, D-50939 Koeln
Universitaet zu Koeln  /\/\...    \ Tel. +49 (0)221 470-4543, Fax -4900
_______________________L|L|__|_____\ http://www.uni-koeln.de/deiters/

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