Color Management

[vifino]

Description

Hey! I'd love to see color calibration/correction on Hyprland as well.

Specifically, a way to load an ICC profile per monitor to make normal SDR monitors display sRGB decently, making multi-monitor use suck less.

Plasma 6 seems to have implemented this, allowing correction for sRGB color space along with HDR/REC.2020.

While the proposed wayland protocol isn't merged, it does seem to be inching closer and closer as well.

This relates to #3423, which assumed lack of support for color management (with colord, specifically) was a bug.
I don't think so, but I'd sure love to have this!

[vaxerski]

doubt I'll impl this before the proto gets merged because I want wlroots to impl it for a guideline on how to do it. I have no clue how icc works

[Sinaaaa]

Description

Hey! I'd love to see color calibration/correction on Hyprland as well.

Specifically, a way to load an ICC profile per monitor to make normal SDR monitors display sRGB decently, making multi-monitor use suck less.

Plasma 6 seems to have implemented this, allowing correction for sRGB color space along with HDR/REC.2020.

While the proposed wayland protocol isn't merged, it does seem to be inching closer and closer as well.

This relates to #3423, which assumed lack of support for color management (with colord, specifically) was a bug. I don't think so, but I'd sure love to have this!

It's possible to use Gnome's lacking implementation already & if they eventually figure this one out, then it might just continue working the same way as now.
Basically you set your ICC profile in Gnome & then you log into Hyprland with GDM and the display manager will keep the profile going to the same extent it is applied in Gnome Wayland. (works in other WLR window managers as well)

[vifino]

wlroots seems to have a MR open that implements the simple color correction and profile loading: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4280

Seems unrelated to the protocol however.

[blitzgneisserin]

If you have a wide gamut screen and absolutely need color management for the colors not to look oversaturated, you can use a profile that contains only profiling data and no calibration curves. You can set the icc profile inside firefox, and some other color managed apps such as geeqie, digikam/showfoto, darktable, rawtherapee etc. You cannot set display icc profiles in other browsers than firefox though. However, if your screens color space is very similar to p3, e.g., then you can choose p3 in chromium e.g., because that's built in.

[xz-dev]

As a modern display system, this is absolutely indispensable.

[vaxerski]

if you need it so much you can write a screen shader that implements the color correction. That's what hyprland would be doing anyways once this is implemented.

[blitzgneisserin]

Well, implementing color management does not make sense at the moment because clients (apps), such as firefox, Gwenview etc cannot communicate with the wayland color management engine yet.
Loading calibration curves and profiling data from an icc file is already implemented in sway-git, but a) it does not work properly yet b) clients cannot communicate with the protocol yet.

I think it's a bit more than just a screen shader. I will post the sway commits in a moment.
Anyway, it's already implemented in wlroots.

[blitzgneisserin]

swaywm/sway@40ca415

[blitzgneisserin]

Just one more remark: well, we are waiting for the first clients to implement system wide wayland color management, afik they don't exist yet. Sebastian Wicks talk at LGM2024 was about this topic but the graphics devs still seem to be rather skeptical.
Just have a closer look at it and try to understand how this works. I think most LGMers did not understand it.
At the moment, what works best on wayland is profiling only and setting the profile inside the client (letting the client do color management the old x11 way).
Anyway, you will have to deal with this properly if you want to support hdr screens.

[vaxerski]

I don't see how clients are involved here at all, the only idea I can see is an app (idk a game?) being able to send to the compositor what ICC profile to load.

The wlroots MR in question seems to me like it does exactly what I'd suspect, loads the ICC stuff and transforms the colors at the output with a shader:

https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4280/diffs#7324c2d10e1b31e3e01184df744e243ce94bb071

I do not write vulkan and I've never done ICC but it seems to me like all it is, is just transforming the final image.

Further reinforced by this: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4693

Since when you use a color transform, you have to re-render the image and can't push it straight to the gpu.

[vaxerski]

HDR is sent differently yes, and once #6608 is done I am planning to do some HDR stuff eventually, though no immediate plans.

After the full migration (and some bugfix period) I want to push HW plane support into aquamarine and get Hyprland to use hw planes as much as possible. They have a huge performance/battery life potential and more people would benefit from it than ICC or HDR, IMHO.

letting the client do color management the old x11 way

IMO it's the better approach. For many apps, 100% color accuracy is redundant and useless. (idk a file manager) and the disadvantage of having to do an extra pass where you could use direct scanout is a major con.

[blitzgneisserin]

Well clients are involved since they need to tell the compositor in which color space the image they show is. Also applies for e.g. a web browser. The compositor/wayland does the actual color management.
The sutuation is as follows at the moment: everything is displayed as srgb. If wayland does not know in which color space the image is, in thinks it is in srgb. Colors outside of srgb cannot be displayed.
Many displays nowadays have a larger color space than srgb, mostly something like adobergb or p3, especially smartphones and tablets. They can show more and more saturated colors. If the compositor thinks the screen is srgb, the colors look oversaturated.
On x11, if you are using a wide gamut screen, and apps such as browser and image viewer are doing color management, everything outside those color managed programs looks oversaturated, e.g. desktop background, (desktop) icons, colored text etc.
Images usually have a color space embedded, e.g. srgb or adobergb.
System wide color management is functional since a long time on macos.
How could I explain this better? Wayland knows the image is in srgb and the screen is in adobergb, it desatures the image, wayland knows image and screen are in srgb, it does nothing, wayland knows image in one window is in rec2020, and in the other is is srgb, the screen is adobergb, it makes window 1 more satureted and window 2 less saturated. Afaik there is also the possibility that wayland lets a certain window do the color management.
The most annoying thing about this is at the moment probably the desktop background, if there is no system wide color management, the wallpaper needs to be converted to the displays color space every time
At the moment hyprland assumes that everything is in srgb, but that's not good in the long run. Making it assume that everything is p3 or any other larger color space is not good either. Screens and images/ videos/games can be/have many other color spaces.
Assuming srgb will not work with hdr screens, everything that is not color managed will look terrible.
If hyprland has an hdr mode, non hdr content will look bad when hyprland is in hdr mode, basically there will be very little satuation and contrast.

[blitzgneisserin]

the only idea I can see is an app (idk a game?) being able to send to the compositor what ICC profile to load.

Exactly, that's it.