[RFC wayland-protocols] Color management protocol

[Niels Ole Salscheider]

On Friday, 9 December 2016, 11:20:14 CET, Bill Spitzak wrote:
> On Fri, Dec 9, 2016 at 5:29 AM, Niels Ole Salscheider
> 
> <niels_ole at salscheider-online.de> wrote:
> > Applications that care a bit more about color correction (but do not have
> > professional needs) could convert all their colors to the blending color
> > space of the compositor. I'd expect this blending color space to be
> > linear if the compositor cares about good colors.
> > This would have the advantage that the compositor does not have to do the
> > conversion "application output color space -> blending color space".
> 
> Actually it is quite likely that the compositor may use a "blending
> space" that is *not* the preferred colorspace of the buffers. For
> instance just using OpenGL sRGB sampling for the input and output
> textures will cause a linear "blending space" while all the buffers
> are using sRGB gamma. Even on the CPU it is reasonably efficient to do
> this conversion as part of the composite, especially if you are
> willing to have some inaccuracy in the effective power functions.

Maybe I should reword it then. The intention of allowing to query the blending 
space was to tell applications the preferred color space of a surface. That 
is, if they do any color management they should create surfaces with that 
color space to minimize computing time.

Anyway, this preferred space should probably not be sRGB if the compositor 
cares about accurate colors. This is because there are many monitors that have 
wider gamuts and you would clip the colors at that point.