LPGAMMATABLE _cmsBuildKToneCurve(cmsHTRANSFORM hCMYK2CMYK, int nPoints)
{
LPGAMMATABLE in, out;
LPGAMMATABLE KTone;
_LPcmsTRANSFORM p = (_LPcmsTRANSFORM) hCMYK2CMYK;
// Make sure CMYK -> CMYK
if (p -> EntryColorSpace != icSigCmykData ||
p -> ExitColorSpace != icSigCmykData) return NULL;
// Create individual curves. BPC works also as each K to L* is
// computed as a BPC to zero black point in case of L*
in = ComputeKToLstar(p ->InputProfile, nPoints, p->Intent, p -> dwOriginalFlags);
out = ComputeKToLstar(p ->OutputProfile, nPoints, p->Intent, p -> dwOriginalFlags);
// Build the relationship
KTone = cmsJoinGamma(in, out);
cmsFreeGamma(in); cmsFreeGamma(out);
// Make sure it is monotonic
if (!IsMonotonic(KTone)) {
cmsFreeGamma(KTone);
return NULL;
}
return KTone;
}
// Compute Black tone curve on a CMYK -> CMYK transform. This is done by
// using the proof direction on both profiles to find K->L* relationship
// then joining both curves. dwFlags may include black point compensation.
cmsToneCurve* _cmsBuildKToneCurve(cmsContext ContextID,
cmsUInt32Number nPoints,
cmsUInt32Number nProfiles,
const cmsUInt32Number Intents[],
const cmsHPROFILE hProfiles[],
const cmsBool BPC[],
const cmsFloat64Number AdaptationStates[],
cmsUInt32Number dwFlags)
{
cmsToneCurve *in, *out, *KTone;
// Make sure CMYK -> CMYK
if (cmsGetColorSpace(hProfiles[0]) != cmsSigCmykData ||
cmsGetColorSpace(hProfiles[nProfiles-1])!= cmsSigCmykData) return NULL;
// Make sure last is an output profile
if (cmsGetDeviceClass(hProfiles[nProfiles - 1]) != cmsSigOutputClass) return NULL;
// Create individual curves. BPC works also as each K to L* is
// computed as a BPC to zero black point in case of L*
in = ComputeKToLstar(ContextID, nPoints, nProfiles - 1, Intents, hProfiles, BPC, AdaptationStates, dwFlags);
if (in == NULL) return NULL;
out = ComputeKToLstar(ContextID, nPoints, 1,
Intents + (nProfiles - 1),
hProfiles + (nProfiles - 1),
BPC + (nProfiles - 1),
AdaptationStates + (nProfiles - 1),
dwFlags);
if (out == NULL) {
cmsFreeToneCurve(in);
return NULL;
}
// Build the relationship. This effectively limits the maximum accuracy to 16 bits, but
// since this is used on black-preserving LUTs, we are not loosing accuracy in any case
KTone = cmsJoinToneCurve(ContextID, in, out, nPoints);
// Get rid of components
cmsFreeToneCurve(in); cmsFreeToneCurve(out);
// Something went wrong...
if (KTone == NULL) return NULL;
// Make sure it is monotonic
if (!cmsIsToneCurveMonotonic(KTone)) {
cmsFreeToneCurve(KTone);
return NULL;
}
return KTone;
}
