Re: [csswg-drafts] [css-color-4] Channel clipping breaks author expectations, especially when using 'perceptually uniform' spaces (#9449)

If the concern is about color formats that give easy access to a very wide gamut, rather than a concern with adapting those colors for display, then browsers shipped the wrong half of the spec. Now authors are encouraged to use the _fully interop/supported_ wide gamut formats, and there's absolutely no safety net in place to ensure those formats work for people on the other end. This is what has me confused.

> > We can't put this on authors, and expect them to _just keep all their colors in the gamut_.
> 
> I agree with this statement. It shouldn't be expected that an author ensure that all colors be in the gamut of the target device.

In that case, a solution that is specific to (ok)l** formats is not a solution to this issue. We can't 'bake gamut mapping' into a few wide-gamut formats and be done with it. We would still need gamut mapping for other wide-gamut formats, which may still render on narrower-gamut displays. If we want to _also_ change how a few formats work, that should be a separate issue for discussion.

Trying to move gamut mapping forward, I see a few options on the table.
- If the priority is to _preserve lightness and hue, at the expense of chroma_ (this matches my experience in the field, but my experience is not universal) the current spec does that decently well using oklch and ΔEOK. 
  - In the thread above, @facelessuser points out some tradeoffs with oklch vs lch as the base model, which would warrant a a side-by-side comparison and decision. 
- Is there a solid counter-proposal for a multi-channel mapping algorithm? Can we bring examples to a telecon, and discuss the tradeoffs that we're willing to make?
- The other hinted-at suggestion, which I may be reading incorrectly, is that different formats _represent different authors intents_ in some heuristic way? Which might lead us to different mapping for different color formats? I can see some logic to that - I would reach for different formats to achieve different goals, but it leads to some strange outcomes:
  - The same out-of-gamut color, on the same narrower-gamut device, is mapped to a different result for reasons that may not be obvious. 
  - On the plus side, we're providing tools to change the format of a color, so authors would have an escape hatch?
  - Browsers have to maintain several mapping algorithms? Is that reasonable?

Did I miss something? Can we narrow in on a path forward?

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Received on Thursday, 25 January 2024 00:18:35 UTC