[sane-devel] Canon LIDE35 color and motor issues
pierre at pirsoft.dnsalias.org
Thu Jan 4 13:37:41 CET 2007
Luke Campagnola schrieb:
> It's been a while since I originally brought this up, but I've pulled out
> the ol' scanner for another go.
> to recap: color calibration isn't quite right on my canon lide35--the dark
> colors drop out to black. I turned on SCAN_FLAG_DISABLE_SHADING as you
> instructed, and as you predicted this recovered my lost dark colors. Where
> should I go from here? Should I crank up SANE_DEBUG_GENESYS and send you
> scanimage output and *.pnm files?
> Thanks, Luke
Did you try with sane from cvs? There have been some bug fixes. If that
does not show the dark colors, use SANE_DEBUG_GENESYS=255 and
SANE_DEBUG_GENESYS_GL841=255 with scanimage in color mode, and send the
resulting error output and the generated .pnms.
> On 3/7/06, Pierre Willenbrock <pierre at pirsoft.dnsalias.org> wrote:
>> > - Color reproduction is better with the sane driver than the windows
>> > which tends to boost the reds way too much (yaay)
>> > - Brightness reproduction is quite poor with the sane driver. It seems
>> > darker colors just drop off to black very quickly.
>> A better tool to determine if the bright and dark colors are correctly
>> reproduced is a histogram tool. You can clearly see, if there is still
>> room at the bottom and top of the histogram(not too much, as you still
>> want some useable color values ;-)).
>> This reveals that dark colors are cut off for the sane driver, but it
>> also shows that the windows driver cuts off bright colors.
>> Anyway, it shows a incorrect calibration on the sane side.
>> To get an unshaded image, you can disable shading correction in
>> gl841_init_regs_for_scan by changing the flags(last parameter to
>> gl841_init_scan_regs, currently 0) to include SCAN_FLAG_DISABLE_SHADING.
>> If the image then still shows dark colors cut off, the offset/exposure
>> calibration is to blame. Otherwise the shading calibration calculates
>> incorrect data(which i suspect).
>> I should put this lengthy description online somewhere..
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