[Development] HDR Support in Qt and Angle

Boudewijn Rempt boud at valdyas.org
Mon Nov 26 14:01:10 CET 2018

On maandag 26 november 2018 13:14:12 CET Allan Sandfeld Jensen wrote:

> It depends on what you want. Using Display P3 for instance is just
> wide-gamut not HDR. You can get that with just the new color-space support
> and higher non-extended color precision. That is the primary motivation for
> doing that first as wide-gamut monitors are already on the market and in
> the hands of many (high-) end-users. Where HDR is still mostly
> non-standardized on PC monitors.

We're specifically working on support for the VESA DisplayHDR standard: 
https://displayhdr.org/ . I'm testing with a ASUS ROG Swift PG27UQ monitor. 

> The use of extended RGB, as scRGB is also known, is very useful behind the
> scenes in any case, as using that you can map to and from any color-space
> without clamping, so we can keep something that is internally like sRGB,
> while still supporting wide-gamut by later taking the extended-sRGB and
> turning it back into a non-extended wide-gamut image. This makes it
> possibly to put the clamping and final color-space conversion in the QPA,
> while keeping the rest generic. So I would still support at least
> linear-scRGB (aka extended-linear- sRGB), even if only as an intermediate
> format.
> It is arguably a strange non-sensical format with many impossible colors,
> but it is also very useful.
> Also doesn't BT.2020 also require extended color-values above (1.0, 1,0,
> 1.0) in most encodings?

Well... We're not doing image manipulation using Qt classes. We simply have a 
buffer, handle that using opencolorio (which has suddenly seen a huge amount 
of development) to generate another buffer that gets stuffed into f16 textures 
and displayed. The amazing thing is that we've actually massaged Angle and Qt 
into making that possible using QOpenGLWidget.

The result is a set of patches that we want to clean up and upstream :-)

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