I have just uploaded to the Gimp plug-in repository a plug-in that enables
you to modify the color temperature of a photo. I can be used to correct
the bluish cast in overcast photos, or even (to some extent) the red cast in
photos taken under incandescent light with the camera set to daylight.
At least for me, the plugin works better than playing around with the levels
and curves menus by hand, in part because the color transformations are done
in the linear (rather than gamma-corrected) color space, and use black-body
color temperature as reference.
Anyway, I had been wishing for a long time for a tool to modify the color
temperature of an image, and now there is one!
I hope it can be useful to others! Give it a try, it has extensive help
All the best,
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