Bug#454402: Problem investigation results
Upon some investigation I managed to find the reason of scanned image
artifacts. It was indeed JPEG compression, which occured before
transferring image to computer, in order to speed up process. I also
discovered that JPEG compression became default setting for hpio
backend only recenty.
A [working, but ugly] solution is to tweak file
~/.sane/.xsane/your-super-scanner.drc, changing the value of
"compression" parameter. I have set it to "none", and artifacts gone.
Note however, that it a) works for only one user and b) works only if
you use xsane frontend. I sometimes use scanimage frontend, so it's
crucial that I do not forget to specify --compression=none option.
That's real PITA.
Also note that xsane GUI has no control for the option (you have to
edit drc file).
I'm absolutely sure there must be a way to specify compression type on
backend level. The information on compression parameter should be
clearly stated in backend manual.
Andrey
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