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Gamut mapping #443
Description
Description
CSS Color 4 describes how out of gamut colors must be mapped to an RGB destination.
However no browser currently implements this.
Browsers however do implement various features that give access to wide gamut and out of gamut colors.
Because the general syntax is supported, it is not possible to use feature detection. @supports (color: oklch(<some out of gamut color>)) {} only indicates if the syntax is supported, not if the browser fully and correctly supports the specific value.
The longer the delay to shipping gamut mapping the more problematic it will be for developers and end users.
If there was a way to do feature detection developers could use known fallback mechanics and use progressive enhancement. Without this developers will have to wait for usage of the affected browser versions to drop below specific thresholds. The longer browsers wait with implementation, the more versions are affected, the longer developers will have to wait.
Specification
https://www.w3.org/TR/css-color-4/#css-gamut-mapping
Open Issues
No response
Tests
Current Implementations
- Blink
- Gecko
- WebKit
Standards Positions
No response
Browser bug reports
https://bugs.chromium.org/p/chromium/issues/detail?id=1439722&q=gamut%20mapping&can=2
https://bugzilla.mozilla.org/show_bug.cgi?id=1847503
https://bugs.webkit.org/show_bug.cgi?id=261603
there are more, but these are some I know of
Developer discussions
No response
Polls & Surveys
No response
Existing Usage
No response
Workarounds
postcss-preset-env can convert out of gamut colors with the correct gamut mapping method.
However this restricts these features to static values.
Any value coming from JavaScript, user input or var() can not be converted with build tools.
Accessibility Impact
Because clipping (the current flawed behavior) can produce much darker colors than intended it is highly likely that contrast of content is affected, making content less accessible.
Correctly implementing gamut mapping will also be needed for contrast-color() which is first and foremost an accessibility feature.
i.e. fixing this will fix some issues and will make future accessibility work easier.
Privacy Impact
none
Other
Technically this is part of css-color-4 which is already a focus area.
However given the nature of the issue I think it would be best to call specific attention to it.
Activity
LeaVerou commentedon Oct 9, 2023
Related: https://twitter.com/LeaVerou/status/1711223584603901975
dholbert commentedon Oct 16, 2023
Possibly just a subset of #426 (which includes the linked WPT test)
romainmenke commentedon Oct 16, 2023
Tests need to cover :
color(),lch(), ...)color-mix())challenges :
svgeesus commentedon Oct 18, 2023
Unrelated. The results of RCS are not gamut mapped at computed value time, only as used values.
gsnedders commentedon Oct 26, 2023
We should probably have some discussion wrt our infrastructure here. Currently the macOS runs are running with sRGB colour space at the system level, I don't know what the status of our Ubuntu images are? @jgraham? (This clearly doesn't help with testing things that are expecting output on a wider-than-sRGB either way, but that would at least mean we can deterministically test the sRGB output subset.)
svgeesus commentedon Oct 26, 2023
Perhaps we need a flag for any tests that assume a wide-gamut screen or that require an sRGB screen.
svgeesus commentedon Oct 26, 2023
Maybe also add some authoring advice, for example when testing wide gamut color formats, start with an sRGB color then convert it for the test, so the displayed result does not need gamut mapping on an sRGB test screen.
wpt-interop commentedon Feb 1, 2024
Thank you for proposing Gamut mapping for inclusion in Interop 2024.
We wanted to let you know that this proposal was not selected to be part of Interop this year.
We are still missing test infrastructure for testing Gamut mapping. Please note this should not be taken as a comment on the technology as a whole, and once the test infrastructure issues are resolved, we would welcome this proposal being resubmitted for a future round of Interop.
For an overview of our process, see proposal selection. Thank you again for contributing to Interop 2024!
Posted on behalf of the Interop team.
dandclark commentedon Feb 1, 2024