Re: [csswg-drafts] [css-color] D50 mismatch in Lab ↔ sRGB algorithms

> I've seen many variations on the matrices used to get sRGB ↔️
XYZD65 ↔️ XYZD50, or direct sRGB ↔️ XYZD50 pairs

Firstly, you can't do any of those with just a matrix; the sRGB needs to be linearized first. But having done that step, the operations for lin_sRGB to XYZ_D65, and XYZ_D65 to LMS, and white adjustment, and LMS to XYZ_D50 are all 3x3 matrices so the overall matrix is obtained by matrix multiplication.

The slightly different value for the Z component of D50 in ICC [is a mistake, not an intentional change](https://lists.w3.org/Archives/Public/public-colorweb/2018Apr/0003.html), but one they are now unable to correct without requiring all deployed CMS to be updated. 

I feel that it would be better to express the correct values in the spec, with enough significant digits to avoid roundoff error.

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Received on Tuesday, 3 April 2018 01:43:02 UTC