Øyvind Kolås wrote:
> On Nov 27, 2007 7:00 PM, Stephane Chauveau
> <[EMAIL PROTECTED]> wrote:
>> Øyvind Kolås wrote:
>>> You could start out by studying the following paper, as well as it's
>>> /Øyvind K.
>> Nice article. The following Wikipedia pages does not describe so many
>> methods but are probably easier to start with:
>> The following article is even less technical but is also a nice read and
>> it explains the most common issues with automatic WB.
>> Anyways, a plug-in providing several WB methods would be cool but, in
>> most cases, I believe that it would be even better to extend the Color
>> Balance tool with the ability to manually pick the grey point in the
>> image. The easiest way to implement that feature could be to add a 'Set
>> White Point' button to the Color Picker tool.
> This functionality exists in the levels tool already.
Nice! I never noticed that the grey point picker in the level tool could
be used to adjust the WB. It is unfortunately limited to the mid-tones.
The behavior I have in mind is quite different and is more like the one
found in most cameras and described in the paper you mentionned (the Von
Kries hypothesis): figure out a grey point to compute a set of 3
coefficients (for red,green and blue) and multiply each channel by its
respective coefficient (with clipping). See for example how WB can be
done in UFraw by selecting a grey area with the mouse.
> Personally I'd prefer a gui similar to:
> for a combined levels (on luminance) and white point/gray point/black
> point offset. Since I don't find it entirely natural to modify the
> white point using levels.
Me neither. The grey/white point in white balance (the illuminant tint)
and the grey point in levels (the average brightness) are very different
> /Øyvind K. (Doing full quote and replying to the list since the
> message I reply to didn't seem
> to be sent to the list.)
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