Re: [csswg-drafts] [css-color-4] Define epsilon (or range of valid epsilons) for determining when Lab/OKLab should be considered achromatic (#11706)

Maybe it will help if I illustrate my confusion.

Consider Lab which has a reference range of 125 and -125. In Lab the threshold would be (125 - -125) / 100,000 = 0.0025.

I assume then the a and b component are compared to this threshold, so `lab(50% 0.0025 0.0025)` is on the edge of this threshold.

The reference range for LCh is 150 for chroma, 150 / 100,000 = 0.0015.

If we convert `lab(50% 0.0025 0.0025)` to LCh, we get `lch(50% 0.00354 45)` which exceeds the achromatic threshold in LCh. Is that desired? Do we care that LCh and Lab, which represent the same space, but in different coordinates, have a difference in what they consider achromatic?

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Received on Thursday, 27 March 2025 17:18:25 UTC