Wayland compositor color management model

Hi all,

the recent discussions with Simon Thompson and others have given me
inspiration to think about how Wayland should account for in-display
image adjustments which lead me to write
https://gitlab.freedesktop.org/pq/color-and-hdr/-/merge_requests/35

(Best viewed at
https://gitlab.freedesktop.org/pq/color-and-hdr/-/blob/bb44957a29c49232c3f94530e92617f6e8fc9d36/doc/color-management-model.md
)

That concept may be useful also for the W3C, because it may well be
what Linux desktop OSs offer to browsers in terms of color support.

It starts by stating that a Wayland compositor will only convert
display-referred signal to display-referred signal, but that is a
little bit of a lie, because I do believe we will also support HLG.
Therefore, when the image content or the monitor signal is in HLG, drop
the unnecessary display and viewing condition referrals.

We take care to consider also the traditional color management (ICC)
use cases where exact light colorimetry must not be ruined with the
perceptional conversions that are otherwise desired.

I hope this can provide what browsers need. Any comments are welcome.


Thanks,
pq

ps. I picked my nick in the 90s, it has nothing to do with perceptual
quantizer. :-)