Re: Pre-meeting Thoughts on HDR Canvas

Thanks Chris for correcting me.

I realize this is an old problem, but I think that adding HDR capabilities
to canvas risks exacerbating it greatly because we will end up with
inconsistent blending and gradient interpolation based on the canvas's
working profile.
For example, if a hypothetical app selects a canvas working profile to
match the output device's capabilities, these behavior discrepancies risk
being perceived as bugs and will be unpleasant to work around for web
developers.

On Wed, Jan 27, 2021 at 12:46 PM Chris Lilley <chris@w3.org> wrote:

>
> On 2021-01-27 18:32, Justin Novosad wrote:
> > The CSS and SVG specifications do not explicitly address the issue of
> > gamma-correct blending, but the examples in the CSS spec suggest doing
> > things the "wrong" way, which ignores gamma correctness.
>
> The SVG specification explicitly says that filer operations are in
> linear-light sRGB by default (with an option to change to sRGB, where
> speed is more important than getting the right result); and that all
> other operations are (sadly) in gamma-encoded sRGB by default (with an
> opt-in for linear-light sRGB).
>
> The CSS Compositing specification, sadly, requires operations in
> gamma-encoded sRGB. This choice was primarily driven by backwards
> compatibility with existing content; and secondarily with compatibility
> of blend modes, as popularized in Adobe Photoshop, which are also
> computed in gamma-encoded RGB spaces.
>
> CSS Compositing thus needs to add an opt-in for linear-light compositing.
>
> --
> Chris Lilley
> @svgeesus
> Technical Director @ W3C
> W3C Strategy Team, Core Web Design
> W3C Architecture & Technology Team, Core Web & Media
>
>
>