[Gimp-user] GIMP-2.10 and GIMP2.99 are still sRGB-only image editors

[Elle Stone <ellestone ninedegreesbelow com>]

A misconception I keep seeing on various forums needs to be corrected:

GIMP-2.10 does *NOT* produce correct editing results in color spaces 
other than sRGB. Neither does GIMP-2.99.

Editing in AdobeRGB, ProPhotoRGB, Rec2020, etc WILL produce *wrong* 
results for many operations, and unless you are thoroughly conversant 
with the underlying code, or else have a way to compare results with a 
properly color-managed editing application, you don't have any way to 
know what's right and what's wrong. It's best to stick with editing only 
in GIMP's built-in sRGB color spaces.

The same is true if you are using GIMP-2.99: Some things that don't work 
in GIMP-2.10, do work in GIMP-2.99. Other things that actually do work 
in GIMP-2.10, don't work in GIMP-2.99.

About two years ago major changes were made in babl and additional 
changes were made in GIMP-2.99, messing up stuff that still works in 
GIMP-2.10. For awhile progress was being made in GIMP-2.99 on extending 
the arena of "what actually works", some of which progress is from bug 
reports I filed and in some cases helped to fix - it seems nobody else 
was testing the new code to see what actually did work.

I was able to write code that fixed some of the bugs I reported for 
GIMP-2.99 color management. But once I reached the point where further 
coding requirements exceeded my coding ability, progress simply stopped, 
with everyone else saying "some day" proper color management for GIMP 
would be a priority. I began to feel like the best way to make sure a 
bug would never get fixed, was to have the dreaded "Concepts: Color 
Science" tag attached to it.

Since autumm of 2013 I've been participating in GIMP development, mostly 
in the area of color management (editing in color spaces other than 
sRGB) and color science (making sure GIMP code produces correct results 
for things like layer blend modes, Curves and Levels, AutoStretch, 
Luminance, and so on; and adding code for things like LCh color pickers 
and blend modes).

Participating in GIMP development used to be challenging and enjoyable. 
But over the last couple of years my interest in and patience with the 
slow pace of progress regarding GIMP color management have dwindled to 
the point of disappearing altogether.

If someone else feels like helping with GIMP color management and color 
science, here's a list of still-open bug reports that I reported after 
the migration to gitlab, most of which have to do with color 
management/color science:

https://gitlab.gnome.org/GNOME/gimp/-/issues?scope=all&utf8=%E2%9C%93&state=opened&author_username=ellestone

Here are bugs that I opened before the migration to gitlab:
https://gitlab.gnome.org/GNOME/gimp/-/issues?scope=all&utf8=%E2%9C%93&state=opened&author_username=bugzilla-migration&search=ellestone

The most important color management bugs still open from before the 
migration to gitlab are these:

* Replace hard-coded sRGB parameters to allow editing in other RGB 
working spaces (opened 6 years ago): 
https://gitlab.gnome.org/GNOME/gimp/-/issues/594 - in some ways this bug 
is obsolete as current GIMP color management issues are less about 
actual hard-coded values and more about a lack of any way to convey the 
required "not sRGB" color space information to various sections of code 
that need this information.

* Decomposed to LAB images have the wrong ICC profile assigned (opened 4 
years ago): https://gitlab.gnome.org/GNOME/gimp/-/issues/883

* Address various limitations of LCMS soft proofing (opened 4 years 
ago): https://gitlab.gnome.org/GNOME/gimp/-/issues/976
the
and hoping very much that GIMP will find new developers that them a lot 
of energy and some interest and expertise in color management and color 
science.
* Support for high bit depth RGB (and LCH?) color palettes for painting 
(opened 2 years ago): https://gitlab.gnome.org/GNOME/gimp/-/issues/1328

Similar searchs in https://gitlab.gnome.org/GNOME/gegl/ and 
https://gitlab.gnome.org/GNOME/babl/ will turn up a few additional color 
management issues.

Best of luck to all,
Elle Stone

--
https://ninedegreesbelow.com
Color management and free/libre photography