Re: PQ HDR in PNG - draft review

On Sat, May 20, 2017 at 5:20 AM, Lars Borg <borg@adobe.com> wrote:

> Hi Fredrik,
>
>  ICC version 4.x is too difficult to implement efficiently
>
>
> Interesting observation.
> Does this apply to the mandatory parts or only to the optional parts?
> Can you elaborate?
>
>

For chrome to do  color management efficiently, everything needs to be done
on the GPU.
Tables are generally much less efficient than doing using math on the GPU,
and my impression
is that ICC v4 relies much more heavily on tables than ICC v2. It's been a
while since I read the
ICC spec, so I don't remember which parts are mandatory.

     /Hubbe



> AFAIK PQ or HLG cannot be implemented accurately in ICC v2, as there’s no
> way to handle overrange.
> The v4 para tag enables accurate overrange
>
> Lars
>