[sane-devel] pixma: no gamma table in TPU mode

m. allan noah kitno455 at gmail.com
Mon May 24 17:31:56 UTC 2010

The driver should disable the gamma table option when it is switched
to TPU mode, if this capability is not available. Support for the
8800F is quite new, so I am not surprised to see these sorts of
issues. Perhaps Gernot will chime in?


On Sat, May 22, 2010 at 2:06 PM, Valentin David
<valentin.david at gmail.com> wrote:
> I actually discovered that XSane can do the gamma correction in
> software. However you have to manually uncheck a box. It should
> automatically detect it cannot send a gamma table, but fails. Is it
> the mistake of XSane or of the driver?
> On Sat, May 22, 2010 at 6:35 PM, Valentin David
> <valentin.david at gmail.com> wrote:
>> I had troubles making the gamma correction to work in transparency
>> unit mode on my Canon 8800F. Since the problem appeared both on
>> xscanimage and XSane, I thought it was probably the driver. So I
>> looked the driver source, and understood that in TPU, the scanner does
>> not get any gamma table but rather sends 48 bits data.
>> I also discovered that it was using a gamma table in flatbed mode. I
>> tried, and then it does work. Which confirms the thing.
>> This is great to get raw data. However it seems that the gui frontends
>> do not tell you cannot set a table. And also, I cannot use GIMP
>> directly. On underexposed or overexposed films, I get quantization
>> artifacts. I need to reinstall CinePaint. :(
>> In XSane, the color correction also gets strange. I do not know if it
>> is related. The red looks overexposed, green OK, and blue under
>> exposed.
>> Certainly the driver needs to say if the gamma correction will be done
>> or not. And the frontend should apply it on its own if there is no
>> correction done. At least for the user not to get this unexpected
>> behavior.
>> --
>> Valentin David
>> valentin.david at gmail.com
> --
> Valentin David
> valentin.david at gmail.com
> --
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