// Compute K -> L* relationship. Flags may include black point compensation. In this case,
// the relationship is assumed from the profile with BPC to a black point zero.
static
cmsToneCurve* ComputeKToLstar(cmsContext ContextID,
cmsUInt32Number nPoints,
cmsUInt32Number nProfiles,
const cmsUInt32Number Intents[],
const cmsHPROFILE hProfiles[],
const cmsBool BPC[],
const cmsFloat64Number AdaptationStates[],
cmsUInt32Number dwFlags)
{
cmsToneCurve* out = NULL;
cmsUInt32Number i;
cmsHTRANSFORM xform;
cmsCIELab Lab;
cmsFloat32Number cmyk[4];
cmsFloat32Number* SampledPoints;
xform = _cmsChain2Lab(ContextID, nProfiles, TYPE_CMYK_FLT, TYPE_Lab_DBL, Intents, hProfiles, BPC, AdaptationStates, dwFlags);
if (xform == NULL) return NULL;
SampledPoints = (cmsFloat32Number*) _cmsCalloc(ContextID, nPoints, sizeof(cmsFloat32Number));
if (SampledPoints == NULL) goto Error;
for (i=0; i < nPoints; i++) {
cmyk[0] = 0;
cmyk[1] = 0;
cmyk[2] = 0;
cmyk[3] = (cmsFloat32Number) ((i * 100.0) / (nPoints-1));
cmsDoTransform(xform, cmyk, &Lab, 1);
SampledPoints[i]= (cmsFloat32Number) (1.0 - Lab.L / 100.0); // Negate K for easier operation
}
out = cmsBuildTabulatedToneCurveFloat(ContextID, nPoints, SampledPoints);
Error:
cmsDeleteTransform(xform);
if (SampledPoints) _cmsFree(ContextID, SampledPoints);
return out;
}
// Joins two curves for X and Y. Curves should be monotonic.
// We want to get
//
// y = Y^-1(X(t))
//
cmsToneCurve* CMSEXPORT cmsJoinToneCurve(cmsContext ContextID,
const cmsToneCurve* X,
const cmsToneCurve* Y, cmsUInt32Number nResultingPoints)
{
cmsToneCurve* out = NULL;
cmsToneCurve* Yreversed = NULL;
cmsFloat32Number t, x;
cmsFloat32Number* Res = NULL;
cmsUInt32Number i;
_cmsAssert(X != NULL);
_cmsAssert(Y != NULL);
Yreversed = cmsReverseToneCurveEx(nResultingPoints, Y);
if (Yreversed == NULL) goto Error;
Res = (cmsFloat32Number*) _cmsCalloc(ContextID, nResultingPoints, sizeof(cmsFloat32Number));
if (Res == NULL) goto Error;
//Iterate
for (i=0; i < nResultingPoints; i++) {
t = (cmsFloat32Number) i / (nResultingPoints-1);
x = cmsEvalToneCurveFloat(X, t);
Res[i] = cmsEvalToneCurveFloat(Yreversed, x);
}
// Allocate space for output
out = cmsBuildTabulatedToneCurveFloat(ContextID, nResultingPoints, Res);
Error:
if (Res != NULL) _cmsFree(ContextID, Res);
if (Yreversed != NULL) cmsFreeToneCurve(Yreversed);
return out;
}