Previously in November 2020 on the mailing list I discussed with @barefootliam (I believe this is his username here) the fact that GIMP as of that time (2.99/2.10) did not seem to support 10-bit per channel color depth on any operating system. Tested were Windows 10, Linux and macOS. A mailing list user Magnus Larsson confirmed this issue. This still seems to be the case as of 2.10.32.
Is there some way to enable support which I am unaware of? If not, are there any plans to implement this? How difficult would it be? Thanks.
I’ve used GIMP since on a system with 10-bit colour + 2 bit alpha.
The problem on Linux back then was that the underlying gtk+ toolkit
didn’t understand 2-bit alpha, so the dialogue boxes tended to have
transparent backgrounds or be invisible. The actual image windows were
fine.
Unfortunately i don’t have a monitor right now to test on, but i’d
suggest trying gimp 2.99 and letting us know what you find.
Was this on Linux? 2.99.12 on macOS and Windows are still not detecting/using 30-bit depth. Linux is less convenient for me to test but I will do so at some point if it would be helpful…
I don’t think macOS or Windows use 10-10-10-2 depth for the desktop, it would break too much (both use transparency all over the place). I’m not positive but I imagine that it is 10-10-10-10 and they just waste the extra bits up to 48-bit or something like that. That may not be the only solution but 2-bit alpha does not match with what I’m seeing.
Did you verify that it was truly displaying 10 bit color rather than the desktop merely being in 10 bit mode? Because GIMP does work with the desktop in 10/30 bit on macOS and Windows, it just doesn’t display 10 bit color.
Thanks. I’ll go back and try it again at some point, but last time I tried on Linux GIMP did the same thing there as on Windows and macOS - not display 10 bit color.
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.
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.
