This shader converts between two color states, by using the
same functions that we use on the cpu. The conversion to perform
is passed as part of the variation.
As premultiplication is part of color states on the shader, we also
encode the premultiplication in the shader.
And because opacity is a useful optimization, we also allow setting
opacity.
For now, the only possible color states are srgb and srgb-linear.
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.
