[sane-devel] Canon LIDE35 color and motor issues

[Pierre Willenbrock]

Pierre Willenbrock schrieb:
> 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
>> the
>> scanimage output and *.pnm files?
>>
>> Thanks, Luke
>>
> 
> Hi 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.
> 
> Regards,
>   Pierre

The patch i attached will not apply -- try this one instead.

> 
>> On 3/7/06, Pierre Willenbrock <pierre at pirsoft.dnsalias.org> wrote:
>>>>  - Color reproduction is better with the sane driver than the windows
>>> driver,
>>>> which tends to boost the reds way too much (yaay)
>>>>  - Brightness reproduction is quite poor with the sane driver. It seems
>>> that
>>>> 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.
>> <snip>
>>
>>> 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..
>>>
>>> Regards,
>>>   Pierre
>>>
> 

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