[Cin] HDR -> sdr tonemap on cpu only

[Andrea paz]

> A HDR (EXR) image is not related to some CMS or color space constraints, its
> luminance level can be arbitrary, unlike HDR video. Here 'HDR' for photo and
> for video is same word, different meaning.

Ah, thank you! That's what I've been missing to understand....
OpenEXR is linear, unlike DPX, precisely so it can be used in the VFX
environment. I was mixing “artificial” luminance values with color
spaces. Now I also understand the values above 1.0 read by the
eydropper tool, which was the thing that confused me the most.
At this point I would be really curious how CinGG plugins work with
hardware and HDR media.