Converting to and from xyz turns out to be more difficult than
expected, depending on what whitepoint you choose, And different
specs choose different whitepoints, so we can't directly map
css xyz to cicp xyz anyway.
This adds machinery to create colorstate objects from cicp
tuples, as well as a function to return a cicp tuple for a
colorstate.
Still missing: a conversion shader for non-default colorstates.
Our conversion machinery supports converting from any color
state to any default color state or back. Direct conversion
between two non-default color states isn't guaranteed. For
converting *to* a cicp color state, we need this function.
Returns the linear color state that renderers should render in when
this is the target color state.
We disable this function unless linear compositing is enabled and just
return @self by default.
This function checks if the colorstate uses an sRGB transfer function
as final operation. In that case, it is suitable for use with GL_SRGB
(and the Vulkan equivalents).
We disable this function (by always returning NULL) unless linear
compositing is enabled, because this function is used to transition
textures and framebuffers to their linear counterparts.
This is mostly an empty shell for now. We only have static instances
for srgb and srgb-linear, which we will use as markers during our
node processing.
In the future, this object may grow more instances, as well as the
ability to create them from and save them to icc profiles or cicp
data. And a color conversion API.
