Hi, That applies to v2 profiles, which have media white not adapted. The goal of this code is to "undo" any chromatic adaptation some v2 profiles (like sRGB and AdobeRGB) have embedded into the matrix. For v2/v4 compatibility sake, media white point in V4 profiles has been adapted to the original iluminant (function ReadCriticalTags in cmsio1.c)
Regards Marti Quoting zetab <[EMAIL PROTECTED]>: > I used wrong encoding in previous post, sorry about that. > > Repost the prevous message: > > I am studying icc profile & cms, and have 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 funcion will generate the transform matrix for converting relative > colorimetric to absolute colorimetric. And before using the white points to > construct the scaling matrix, the function apply chromatic adaptaion on > them. Here is my question, in icc profile 4.2 spec, section 9.2.25 describe > the mediaWhitePointTag as: > > " 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 says that the media white point recorded in profile has already > been adapted to D50, but why the Rel2RelStepAbsCoefs() function adapted the > white point again? Do I have a misunderstanding about the code? > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2008. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > _______________________________________________ > Lcms-user mailing list > Lcms-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lcms-user > ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
