[csswg-drafts] Are a and b in lab( 0%, a, b ) really powerless? [css-color-4] (#6758)

dd8 has just created a new issue for https://github.com/w3c/csswg-drafts:

== Are a and b in lab( 0%, a, b ) really powerless? [css-color-4] ==
> If the lightness of a Lab color is 0%, both the a and b components are powerless

https://drafts.csswg.org/css-color-4/#specifying-lab-lch

Is this true, or is this implementation dependent when the Lab color is mapped to the display color space.
 
`lab( 0%, -100, 100 )` produces an out of gamut sRGB color, which is mapped to a dark color (but not the same dark color) when converted using various convertors:

http://www.brucelindbloom.com/iPhone/ColorConv.html
http://colorizer.org/
https://rufflewind.com/_urandom/colorpicker/

color.js does map `lab( 0%, -100, 100 )` to `rgb(0,0,0)`

Assuming gamut mapping is defined for CSS (https://github.com/w3c/csswg-drafts/issues/5191) won't there still be an implementation dependency if conversion uses ICC profiles? They don't guarantee identical results for out of gamut colors:
https://drafts.csswg.org/css-color-4/#oklab-lab-to-predefined

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/6758 using your GitHub account


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Received on Saturday, 23 October 2021 18:26:01 UTC