Øyvind Kolås wrote: > On Nov 27, 2007 7:00 PM, Stephane Chauveau > <stephane@xxxxxxxxxxxxxxxxxxxx> wrote: > >> Øyvind Kolås wrote: >> >>> You could start out by studying the following paper, as well as it's references: >>> http://www.ivl.disco.unimib.it/papers2003/WB%20Combining%20%20EI%206502-12.pdf >>> >>> /Øyvind K. >>> >>> >> Nice article. The following Wikipedia pages does not describe so many >> methods but are probably easier to start with: >> >> http://en.wikipedia.org/wiki/White_balance >> http://en.wikipedia.org/wiki/Color_temperature >> >> The following article is even less technical but is also a nice read and >> it explains the most common issues with automatic WB. >> >> http://www.cambridgeincolour.com/tutorials/white-balance.htm >> >> 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: > > http://pippin.gimp.org/plug-ins/color_correct/ > > 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 concepts. > /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.) > _______________________________________________ Gimp-developer mailing list Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
