[sane-devel] PIXMA: New option gamma
rolf at bensch-online.de
Fri Feb 10 13:31:07 UTC 2012
Scanning lineart images with scanimage can be a little bit tricky. If
the scanner has problems with the default gamma exponents from pixma.c
or the used subdriver (e.g. pixma_mp810.c)) you should create a gamma
table with gamm4scanimage and use it with scanimage. This is
inconvenient if you are searching for the images's best gamma table.
For normal lineart scans my CS9000F mostly likes a gamma table from the
gamma exponent of 0.7.
Inspired from the epjitsu backend I added a new option gamma. Each time
gamma is used with scanimage the backend generates a new gamma table
from this gamma exponent.
With this patch the backend uses default gamma values as follows:
--custom-gamma=no ==> default gamma from the subdriver
e.g. default gamma is 0.7 from pixma_mp810.c
--gamma-table auto ==> default gamma is 2.2 from pixma.c
--gamma auto ==> default gamma is 0.7
Please try the attached patch and give me a feedback of your scanner's
favorite gamma values.
You can also use xsane to determine the best gamma values of your scanner.
With your feedback I can decide either to adapt the default gamma
exponents or to create a new gamma DEVICE parameter for each scanner.
Xsane is not affected from this patch. After changing some options xsane
always sends an updated gamma table to the backend.
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