Wayland color management

[Dmitry_Kazakov]

@gwgill

If SDR to HDR brightness is specified in (say) cd/m^2, then the HDR luminanceTag would be used to compute the scaling factor.

That was exactly what I was wondering about. When I tested, LCMS2 failed to do the conversions correctly from p2020-pq to p2020-linear. So I’m not sure how many changes are needed there.

@gwgill

Mapping SDR to HDR is pretty simple then - map SDR white to HDR diffuse white. The way it seems to be shaping up in practice is that implementors are simply assuming something like 100 cd/^m is the diffuse white, while nothing in the standards actually specifies this.

There is a small problem with such mapping: in SDR mode Windows maps diffuse white to 80cd/^m, not to 100 cd/^m. And in HDR mode this value is configurable, but is not available to normal desktop applications’ API (yet), it is present only in UWP environment.