Previously in November 2020 on the old mailing list I discussed with @barefootliam the fact that GIMP as of that time (2.99/2.10) did not seem to support 10-bit per channel display color depth (displayed, not the underlying internal image color depth of GIMP) on any operating system. Liam felt that it did partially work but that was not my experience, and a mailing list user Magnus Larsson agreed that it did not work.
Subsequently last year in October I raised the question again on this forum where barefootliam again felt it did work, but @Jehan was unsure of this and suggested that matthiasc might know something about the GTK support at least.
In none of my testing on systems where the 10-bit display is working (verified with a gradient in applications that do support 10-bit) could GIMP display the gradient, Mac, Windows or Linux. I have not gone back and tested again this year because I am assuming there would be some major update or announcement if the work were done for this, which from what Jehan said sounded like it might be no inconsiderable amount of.
To quote Jehan:
As I understand, you are talking about display support, not image storage support, right?
I have no idea if GIMP supports this and I don’t think we have any specific code for 30-bit display. In any case, it likely requires the whole software stack to support this. It means:
- GTK support; I have no idea what’s the current situation. I could find this 1±year-old comment which seems to imply there was no support early 2021 at least. It may have evolved since then. matthiasc could give more input on this.
- Also display backend support (on Linux, it would be X11 or Wayland compositors). For GNOME/Wayland in particular, it looks like this MR would be relevant: Use the first framebuffer config instead of always XRGB8888 (!1756) · Merge requests · GNOME / mutter · GitLab (not merged yet at this point in time).
- And lastly of course, specific application support may be needed (in particular for custom widgets, i.e. canvas — which is after all the most important part where we’d want to show correct colors —, etc. I could imagine, as all common widgets would be handled by the toolkit?). Personally I don’t even have 30-bit hardware to test this. But eventually if I get confirmation the whole stack has support, I’d love GIMP to get proper support.
This being said, it looks like @barefootliam was saying it could already work in some cases? Seriously I have no idea.
So I am checking back in to see if the status of this has changed before I dive into it again myself. 10-bit displays are becoming more and more common, at least ones that support 8-bit+FRC, so I imagine some people may have access to them without even realizing it at this point. I’m not sure of the suitability of FRC displays vs. true 10-bit, but on my one FRC display the results are “similar” between it and a true 10-bit display - in software that supports the 10-bit color depth.
I would definitely consider doing some coding work on this myself, although it sounds like the task may be considerably larger than I have the time or experience (e.g. with GTK internals) to undertake.
[as a new user I can only ping two people per post so I trimmed the ping of matthiasc, if anyone else cares to ping him please do]