GIMP-2.10 from git - wrong tonality when assigning a new ICC profile
An essential function for any image editor is the ability to open an image and assign a new ICC profile, if the embedded profile is wrong, or if there is no embedded profile and the automatically assigned profile is not the correct profile, or even if the user simply wants to assign the "wrong" ICC profile for whatever artistic or other reason.
GIMP used to be able to properly assign ICC profiles. Some time in the last few months or perhaps even longer ago this ability disappeared.
Steps to reproduce:
- Open the attached png file:
-
Promote the precision to 32f gamma precision. Or leave it at 8-bit integer gamma precision. I haven't tested what happens using linear precision.
-
Assign this linear gamma ClayRGB ICC profile:
The colors should get brighter. But for a black and white image they don't change at all:
Starting GIMP-2.10 with the babl transforms disabled does produce correct behavior on assigning a linear gamma ICC profile:
This issue also affects jpegs, tiffs, and ppm files, and so probably all files.
For images with colors (not black and white images), assigning a linear gamma ClayRGB ICC profile to an sRGB image does produce more intense colors, but doesn't produce any change in tonality. So it looks like somehow GIMP is making a new ICC profile that uses the chromaticities of the assigned ICC profile and the TRC of the originally assigned ICC profile. So this bug report is sort of the inverse of #3264 (closed) - in which the image has the wrong colors but the right tonality. Except that this bug for 2.11 seems to affect all images and doesn't require the presence of any DCF tags.
This is for GIMP-2.10 from git updated in the last couple of days, on Gentoo Linux.