I am studying icc profile & color management, and I've read part of lcms 1.17 source code, but there're something confuse me.
In the function "Rel2RelStepAbsCoefs()" in Cmscnvrt.c, as my understanding, this function will generate the transform matrix for converting relative colorimetric to absolute colorimetric. And before using the white points of in&outprofile to construct the matrix, there is a chromatic adaptation operation performing on them.
But according to section 9.2.25 of icc profile spec 4.2, about the mediaWhitePointTag :
" This tag, which is used for generating ICC-absolute colorimetric intent, specifies the XYZ tristimulus values of the media white point. If the media is measured under an illumination source which has a chromaticity other than D50, the measured values must be adjusted to D50 using the chromaticAdaptationTag matrix before recording in the tag. ... ".
The spec say the white point in the profile has already been adapted to D50, and why Rel2RelStepAbsCoefs() adapts the white point again? Do I have a misunderstanding of the source code?
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