33 // This file contains routines for resampling and LUT optimization, black point detection
34 // and black preservation.
36 // Black point detection -------------------------------------------------------------------------
61 // Use darker colorants to obtain black point. This works in the relative colorimetric intent and
69     cmsUInt16Number *Black;  in BlackPointAsDarkerColorant()  local
79     // If the profile does not support input direction, assume Black point 0  in BlackPointAsDarkerColorant()
89    // Try to get black by using black colorant  in BlackPointAsDarkerColorant()
93     if (!_cmsEndPointsBySpace(Space, NULL, &Black, &nChannels)) {  in BlackPointAsDarkerColorant()
118         // Something went wrong. Get rid of open resources and return zero as black  in BlackPointAsDarkerColorant()
123     // Convert black to Lab  in BlackPointAsDarkerColorant()
124     cmsDoTransform(xform, Black, &Lab, 1);  in BlackPointAsDarkerColorant()
144 // Get a black point of output CMYK profile, discounting any ink-limiting embedded
186 // profiles on black point tag, that we must somehow fix chromaticity to
187 // avoid huge tint when doing Black point compensation. This function does
188 // just that. There is a special flag for using black point tag, but turned
212     // v4 + perceptual & saturation intents does have its own black point, and it is  in cmsDetectBlackPoint()
213     // well specified enough to use it. Black point tag is deprecated in V4.  in cmsDetectBlackPoint()
221 …      // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents  in cmsDetectBlackPoint()
239             // If black point is specified, then use it,  in cmsDetectBlackPoint()
247                 // Black point is absolute XYZ, so adapt to D50 to get PCS value  in cmsDetectBlackPoint()
345 // Calculates the black point of a destination profile.
346 // This algorithm comes from the Adobe paper disclosing its black point compensation method.
379     // v4 + perceptual & saturation intents does have its own black point, and it is  in cmsDetectDestinationBlackPoint()
380     // well specified enough to use it. Black point tag is deprecated in V4.  in cmsDetectDestinationBlackPoint()
388 …      // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents  in cmsDetectDestinationBlackPoint()
415         // calculate initial Lab as source black point  in cmsDetectDestinationBlackPoint()
425         // set the initial Lab to zero, that should be the black point for perceptual and saturation  in cmsDetectDestinationBlackPoint()
492 …rve fitting: The round-trip curve normally looks like a nearly constant section at the black point,  in cmsDetectDestinationBlackPoint()
499     // find the black point using the least squares error quadratic curve fitting  in cmsDetectDestinationBlackPoint()