[Lcms-user] Need help recovering the chromaticities that a profile was made with

[Adrian Knagg-B. <aje...@gm...>]

Hi,

I have extracted the chromaticity xy coordinates from a cmsHPROFILE as
follows:

cmsCIEXYZ   *red;
cmsCIEXYZ   *green;
cmsCIEXYZ   *blue;
red   = cmsReadTag (profile, cmsSigRedColorantTag);
green = cmsReadTag (profile, cmsSigGreenColorantTag);
blue  = cmsReadTag (profile, cmsSigBlueColorantTag);
cmsXYZ2xyY(&redxyY, &red);
cmsXYZ2xyY(&greenxyY, &green);
cmsXYZ2xyY(&bluexyY, &blue);

However, if the profile I do this to is a sRGB profile made with
chromaticities from the cmsCIExyYTRIPLE {{0.639998686, 0.330010138, 1.0},
{0.300003784, 0.600003357, 1.0}, {0.150002046, 0.059997204, 1.0}}, and the
standard sRGB whitepoint cmsCIExyY d65_srgb_adobe_specs = {0.3127, 0.3290,
1.0}; I don't get back the same coordinates. Instead I get:

redxyY x: 0.648438, y: 0.330868, Y: 0.222488
greenxyY x: 0.321176, y: 0.597877, Y: 0.716904
bluexyY x: 0.155899, y: 0.066051, Y: 0.060608

What's going on here: is there something I'm not accounting for? And is
there a more correct way to read the original chromaticities back out of a
profile?

Thanks,

Adrian.