HDR support in Wayland/Weston

[Graeme Gill]

Chris Murphy wrote:

Hi Chris,

> I'm pretty sure most every desktop environment and distribution have
> settled on colord as the general purpose service.
> https://github.com/hughsie/colord
> https://www.freedesktop.org/software/colord/

right, but colord is not needed to run X11 color management.
Using ArygyllCMS to load profiles on startup is a viable alternative.
There is also Oyranos.

The experience of trying to get better integration between
colord and color management tools like ArgyllCMS is one of
the things that informs my views on a Wayland color management
protocol. (i.e. it doesn't currently work, even though it
used to at one point.) Having a neutral and consistently
implemented API for color managed clients and color management
tools would be a very good thing.

> By default, colord will create a display profile on-the-fly, for
> attached displays, based on display provided EDID information.

Certainly a useful approach a system may take to providing default
display profiles.

> You'd want to evaluate the interfaces of Argyll CMS and lcms2; it's
> possible you'd use Argyll CMS for profile creation, and lcms2 as the
> transformation engine, for example.

ArgyllCMS's CMM probably isn't a choice for some compositor implementations,
due to its GPL licensing, and current lack of support for ICCV4. I don't think
that it has any noticeable speed advantage of lcms2 for 3 channel conversions
either, and lcms is much better integrated as a drop in CMM. Its plug in
architecture may be an advantage in implementing the HDR tweaks needed,
as well as those wishing to optimize compositor color management performance.

Cheers,
	Graeme.