[Lcms-user] Handling channel extraction

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

Hi,
I'm trying to understand how to handle assignment of a color profile
to a single channel extracted from a colour image that may have an
arbitrary RGB color profile (e.g. extracting the R channel).

Would something like this work, assuming rgb_profile is the
cmsHPROFILE associated with the full RGB image?

cmsHPROFILE extracted_profile == NULL;
if (cmsIsTag(rgb_profile, cmsSigRedTRCTag) && cmsIsTag(rgb_profile,
cmsSigMediaWhitePoint)) {
  cmsToneCurve tonecurve = cmsReadTag(rgb_profile, cmsSigRedTRCTag);
  cmsCIExyY whitepoint = cmsReadTag(rgb_profle, cmsSigMediaWhitePoint);
  extracted_profile = cmsCreateGrayProfile(whitepoint, tonecurve);
}

Thanks,

Adrian.