// 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
LPGAMMATABLE ComputeKToLstar(cmsHPROFILE hProfile, int nPoints, int Intent, DWORD dwFlags)
{
LPGAMMATABLE out;
int i;
WORD cmyk[4], wLab[3];
cmsHPROFILE hLab = cmsCreateLabProfile(NULL);
cmsHTRANSFORM xform = cmsCreateTransform(hProfile, TYPE_CMYK_16,
hLab, TYPE_Lab_16,
Intent, (dwFlags|cmsFLAGS_NOTPRECALC));
out = cmsAllocGamma(nPoints);
for (i=0; i < nPoints; i++) {
cmyk[0] = 0;
cmyk[1] = 0;
cmyk[2] = 0;
cmyk[3] = _cmsQuantizeVal(i, nPoints);
cmsDoTransform(xform, cmyk, wLab, 1);
out->GammaTable[i] = (WORD) (0xFFFF - wLab[0]);
}
cmsDeleteTransform(xform);
cmsCloseProfile(hLab);
return out;
}
// Does create a linear ramp
static
LPGAMMATABLE CreateLinear()
{
LPGAMMATABLE Gamma = cmsAllocGamma(4096);
LPWORD Table = Gamma ->GammaTable;
int i;
for (i=0; i < 4096; i++) {
Table[i] = _cmsQuantizeVal(i, 4096);
}
return Gamma;
}
static
int MostlyLinear(WORD Table[], int nEntries)
{
register int i;
int diff;
for (i=5; i < nEntries; i++) {
diff = abs((int) Table[i] - (int) _cmsQuantizeVal(i, nEntries));
if (diff > 0x0300)
return 0;
}
return 1;
}
// Is a table linear? Do not use parametric since we cannot guarantee some weird parameters resulting
// in a linear table. This way assures it is linear in 12 bits, which should be enought in most cases.
cmsBool CMSEXPORT cmsIsToneCurveLinear(const cmsToneCurve* Curve)
{
cmsUInt32Number i;
int diff;
_cmsAssert(Curve != NULL);
for (i=0; i < Curve ->nEntries; i++) {
diff = abs((int) Curve->Table16[i] - (int) _cmsQuantizeVal(i, Curve ->nEntries));
if (diff > 0x0f)
return FALSE;
}
return TRUE;
}
void _cmsComputePrelinearizationTablesFromXFORM(cmsHTRANSFORM h[], int nTransforms, LPLUT Grid)
{
LPGAMMATABLE Trans[MAXCHANNELS];
unsigned int t, i, v;
int j;
WORD In[MAXCHANNELS], Out[MAXCHANNELS];
BOOL lIsSuitable;
_LPcmsTRANSFORM InputXForm = (_LPcmsTRANSFORM) h[0];
_LPcmsTRANSFORM OutputXForm = (_LPcmsTRANSFORM) h[nTransforms-1];
// First space is *Lab, use our specialized curves for v2 Lab
if (InputXForm ->EntryColorSpace == icSigLabData &&
OutputXForm->ExitColorSpace != icSigLabData) {
CreateLabPrelinearization(Trans);
cmsAllocLinearTable(Grid, Trans, 1);
cmsFreeGammaTriple(Trans);
return;
}
// Do nothing on all but RGB to RGB transforms
if ((InputXForm ->EntryColorSpace != icSigRgbData) ||
(OutputXForm->ExitColorSpace != icSigRgbData)) return;
for (t = 0; t < Grid -> InputChan; t++)
Trans[t] = cmsAllocGamma(PRELINEARIZATION_POINTS);
for (i=0; i < PRELINEARIZATION_POINTS; i++) {
v = _cmsQuantizeVal(i, PRELINEARIZATION_POINTS);
for (t=0; t < Grid -> InputChan; t++)
In[t] = (WORD) v;
cmsDoTransform(h[0], In, Out, 1);
for (j=1; j < nTransforms; j++)
cmsDoTransform(h[j], Out, Out, 1);
for (t=0; t < Grid -> InputChan; t++)
Trans[t] ->GammaTable[i] = Out[t];
}
// Check transfer curves
lIsSuitable = TRUE;
for (t=0; (lIsSuitable && (t < Grid->InputChan)); t++) {
// Exclude if already linear
if (MostlyLinear(Trans[t]->GammaTable, PRELINEARIZATION_POINTS))
lIsSuitable = FALSE;
// Exclude if non-monotonic
if (!IsMonotonic(Trans[t]))
lIsSuitable = FALSE;
// Exclude if weird endpoints
if (!HasProperEndpoints(Trans[t]))
lIsSuitable = FALSE;
// Exclude if transfer function is not smooth enough
// to be modelled as a gamma function, or the gamma is reversed
if (cmsEstimateGamma(Trans[t]) < 1.0)
lIsSuitable = FALSE;
}
if (lIsSuitable) {
for (t = 0; t < Grid ->InputChan; t++)
SlopeLimiting(Trans[t]->GammaTable, Trans[t]->nEntries);
}
if (lIsSuitable) cmsAllocLinearTable(Grid, Trans, 1);
for (t = 0; t < Grid ->InputChan; t++)
cmsFreeGamma(Trans[t]);
}
