A solution for gamma-adjustment support in Wayland

Mattias Andrée maandree at member.fsf.org
Thu Dec 15 15:15:49 UTC 2016

On Thu, 15 Dec 2016 13:18:17 +0100
Kai-Uwe <ku.b-list at gmx.de> wrote:

> > Date: Wed, 7 Dec 2016 13:10:52 +0100
> > From: Mattias Andrée <maandree at member.fsf.org>  
> > ### Abstract ###
> >
> > With the advent of Wayland, our display server has lost
> > a functionality — access to the graphic cards’ colour
> > loop-up tables — that has been used to implement,
> > amongst other things, ergonomic functionality. But we
> > now have a chance to start from scratch and do it the
> > right way.  
> The assumption of a out of band color communication is
> not convenient nor relyable. So colord for ICC stuff in
> wayland is the bad as is currently state. Each window
> system should support proper gamma ramp access and a way
> to transport ICC profiles along the logical monitor
> connection APIs. So far all color relevant display
> systems have evolved like this sooner or later.
> libcoopgamma is GPL. A really unacceptable choice for a
> API, which shall be used by everyone to reach the goal of
> a more structured / disciplined gamma access.

libcoopgamma is just one implementation, anyone can choose
make there library with whatever license they want. And
Wayland should have their own API which libcoopgamma uses
for Wayland support.

> Color correction goes recently more and more into the
> CLUT direction. That is different to the per channel
> gamma APIs you propagate. An abstraction of gamma versus
> CLUT is needed. Effects should not be sticked to a
> particular technology or they will fail in many cases:
> e.g. the need to reinvent this API if one needs a
> desaturated appearance.

I'm aware that per channel ramps is not enough, but it
is available in almost all display servers and is
required for already existing programs. We also need
support for matrices along with the ramps.

> best regards
> Kai-Uwe
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