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+//---------------------------------------------------------------------------------
+//
+// Little Color Management System
+// Copyright (c) 1998-2010 Marti Maria Saguer
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
+// THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+//---------------------------------------------------------------------------------
+//
+
+#include "lcms2_internal.h"
+
+
+#define cmsmin(a, b) (((a) < (b)) ? (a) : (b))
+#define cmsmax(a, b) (((a) > (b)) ? (a) : (b))
+
+// This file contains routines for resampling and LUT optimization, black point detection
+// and black preservation.
+
+// Black point detection -------------------------------------------------------------------------
+
+
+// PCS -> PCS round trip transform, always uses relative intent on the device -> pcs
+static
+cmsHTRANSFORM CreateRoundtripXForm(cmsHPROFILE hProfile, cmsUInt32Number nIntent)
+{
+ cmsContext ContextID = cmsGetProfileContextID(hProfile);
+ cmsHPROFILE hLab = cmsCreateLab4ProfileTHR(ContextID, NULL);
+ cmsHTRANSFORM xform;
+ cmsBool BPC[4] = { FALSE, FALSE, FALSE, FALSE };
+ cmsFloat64Number States[4] = { 1.0, 1.0, 1.0, 1.0 };
+ cmsHPROFILE hProfiles[4];
+ cmsUInt32Number Intents[4];
+
+ hProfiles[0] = hLab; hProfiles[1] = hProfile; hProfiles[2] = hProfile; hProfiles[3] = hLab;
+ Intents[0] = INTENT_RELATIVE_COLORIMETRIC; Intents[1] = nIntent; Intents[2] = INTENT_RELATIVE_COLORIMETRIC; Intents[3] = INTENT_RELATIVE_COLORIMETRIC;
+
+ xform = cmsCreateExtendedTransform(ContextID, 4, hProfiles, BPC, Intents,
+ States, NULL, 0, TYPE_Lab_DBL, TYPE_Lab_DBL, cmsFLAGS_NOCACHE|cmsFLAGS_NOOPTIMIZE);
+
+ cmsCloseProfile(hLab);
+ return xform;
+}
+
+// Use darker colorants to obtain black point. This works in the relative colorimetric intent and
+// assumes more ink results in darker colors. No ink limit is assumed.
+static
+cmsBool BlackPointAsDarkerColorant(cmsHPROFILE hInput,
+ cmsUInt32Number Intent,
+ cmsCIEXYZ* BlackPoint,
+ cmsUInt32Number dwFlags)
+{
+ cmsUInt16Number *Black;
+ cmsHTRANSFORM xform;
+ cmsColorSpaceSignature Space;
+ cmsUInt32Number nChannels;
+ cmsUInt32Number dwFormat;
+ cmsHPROFILE hLab;
+ cmsCIELab Lab;
+ cmsCIEXYZ BlackXYZ;
+ cmsContext ContextID = cmsGetProfileContextID(hInput);
+
+ // If the profile does not support input direction, assume Black point 0
+ if (!cmsIsIntentSupported(hInput, Intent, LCMS_USED_AS_INPUT)) {
+
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ // Create a formatter which has n channels and floating point
+ dwFormat = cmsFormatterForColorspaceOfProfile(hInput, 2, FALSE);
+
+ // Try to get black by using black colorant
+ Space = cmsGetColorSpace(hInput);
+
+ // This function returns darker colorant in 16 bits for several spaces
+ if (!_cmsEndPointsBySpace(Space, NULL, &Black, &nChannels)) {
+
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ if (nChannels != T_CHANNELS(dwFormat)) {
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ // Lab will be used as the output space, but lab2 will avoid recursion
+ hLab = cmsCreateLab2ProfileTHR(ContextID, NULL);
+ if (hLab == NULL) {
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ // Create the transform
+ xform = cmsCreateTransformTHR(ContextID, hInput, dwFormat,
+ hLab, TYPE_Lab_DBL, Intent, cmsFLAGS_NOOPTIMIZE|cmsFLAGS_NOCACHE);
+ cmsCloseProfile(hLab);
+
+ if (xform == NULL) {
+
+ // Something went wrong. Get rid of open resources and return zero as black
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ // Convert black to Lab
+ cmsDoTransform(xform, Black, &Lab, 1);
+
+ // Force it to be neutral, clip to max. L* of 50
+ Lab.a = Lab.b = 0;
+ if (Lab.L > 50) Lab.L = 50;
+
+ // Free the resources
+ cmsDeleteTransform(xform);
+
+ // Convert from Lab (which is now clipped) to XYZ.
+ cmsLab2XYZ(NULL, &BlackXYZ, &Lab);
+
+ if (BlackPoint != NULL)
+ *BlackPoint = BlackXYZ;
+
+ return TRUE;
+
+ cmsUNUSED_PARAMETER(dwFlags);
+}
+
+// Get a black point of output CMYK profile, discounting any ink-limiting embedded
+// in the profile. For doing that, we use perceptual intent in input direction:
+// Lab (0, 0, 0) -> [Perceptual] Profile -> CMYK -> [Rel. colorimetric] Profile -> Lab
+static
+cmsBool BlackPointUsingPerceptualBlack(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile)
+{
+ cmsHTRANSFORM hRoundTrip;
+ cmsCIELab LabIn, LabOut;
+ cmsCIEXYZ BlackXYZ;
+
+ // Is the intent supported by the profile?
+ if (!cmsIsIntentSupported(hProfile, INTENT_PERCEPTUAL, LCMS_USED_AS_INPUT)) {
+
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return TRUE;
+ }
+
+ hRoundTrip = CreateRoundtripXForm(hProfile, INTENT_PERCEPTUAL);
+ if (hRoundTrip == NULL) {
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ LabIn.L = LabIn.a = LabIn.b = 0;
+ cmsDoTransform(hRoundTrip, &LabIn, &LabOut, 1);
+
+ // Clip Lab to reasonable limits
+ if (LabOut.L > 50) LabOut.L = 50;
+ LabOut.a = LabOut.b = 0;
+
+ cmsDeleteTransform(hRoundTrip);
+
+ // Convert it to XYZ
+ cmsLab2XYZ(NULL, &BlackXYZ, &LabOut);
+
+ if (BlackPoint != NULL)
+ *BlackPoint = BlackXYZ;
+
+ return TRUE;
+}
+
+// This function shouldn't exist at all -- there is such quantity of broken
+// profiles on black point tag, that we must somehow fix chromaticity to
+// avoid huge tint when doing Black point compensation. This function does
+// just that. There is a special flag for using black point tag, but turned
+// off by default because it is bogus on most profiles. The detection algorithm
+// involves to turn BP to neutral and to use only L component.
+cmsBool CMSEXPORT cmsDetectBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
+{
+ cmsProfileClassSignature devClass;
+
+ // Make sure the device class is adequate
+ devClass = cmsGetDeviceClass(hProfile);
+ if (devClass == cmsSigLinkClass ||
+ devClass == cmsSigAbstractClass ||
+ devClass == cmsSigNamedColorClass) {
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ // Make sure intent is adequate
+ if (Intent != INTENT_PERCEPTUAL &&
+ Intent != INTENT_RELATIVE_COLORIMETRIC &&
+ Intent != INTENT_SATURATION) {
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ // v4 + perceptual & saturation intents does have its own black point, and it is
+ // well specified enough to use it. Black point tag is deprecated in V4.
+ if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&
+ (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
+
+ // Matrix shaper share MRC & perceptual intents
+ if (cmsIsMatrixShaper(hProfile))
+ return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
+
+ // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
+ BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
+ BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
+ BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
+
+ return TRUE;
+ }
+
+
+#ifdef CMS_USE_PROFILE_BLACK_POINT_TAG
+
+ // v2, v4 rel/abs colorimetric
+ if (cmsIsTag(hProfile, cmsSigMediaBlackPointTag) &&
+ Intent == INTENT_RELATIVE_COLORIMETRIC) {
+
+ cmsCIEXYZ *BlackPtr, BlackXYZ, UntrustedBlackPoint, TrustedBlackPoint, MediaWhite;
+ cmsCIELab Lab;
+
+ // If black point is specified, then use it,
+
+ BlackPtr = cmsReadTag(hProfile, cmsSigMediaBlackPointTag);
+ if (BlackPtr != NULL) {
+
+ BlackXYZ = *BlackPtr;
+ _cmsReadMediaWhitePoint(&MediaWhite, hProfile);
+
+ // Black point is absolute XYZ, so adapt to D50 to get PCS value
+ cmsAdaptToIlluminant(&UntrustedBlackPoint, &MediaWhite, cmsD50_XYZ(), &BlackXYZ);
+
+ // Force a=b=0 to get rid of any chroma
+ cmsXYZ2Lab(NULL, &Lab, &UntrustedBlackPoint);
+ Lab.a = Lab.b = 0;
+ if (Lab.L > 50) Lab.L = 50; // Clip to L* <= 50
+ cmsLab2XYZ(NULL, &TrustedBlackPoint, &Lab);
+
+ if (BlackPoint != NULL)
+ *BlackPoint = TrustedBlackPoint;
+
+ return TRUE;
+ }
+ }
+#endif
+
+ // That is about v2 profiles.
+
+ // If output profile, discount ink-limiting and that's all
+ if (Intent == INTENT_RELATIVE_COLORIMETRIC &&
+ (cmsGetDeviceClass(hProfile) == cmsSigOutputClass) &&
+ (cmsGetColorSpace(hProfile) == cmsSigCmykData))
+ return BlackPointUsingPerceptualBlack(BlackPoint, hProfile);
+
+ // Nope, compute BP using current intent.
+ return BlackPointAsDarkerColorant(hProfile, Intent, BlackPoint, dwFlags);
+}
+
+
+
+// ---------------------------------------------------------------------------------------------------------
+
+// Least Squares Fit of a Quadratic Curve to Data
+// http://www.personal.psu.edu/jhm/f90/lectures/lsq2.html
+
+static
+cmsFloat64Number RootOfLeastSquaresFitQuadraticCurve(int n, cmsFloat64Number x[], cmsFloat64Number y[])
+{
+ double sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0;
+ double sum_y = 0, sum_yx = 0, sum_yx2 = 0;
+ double d, a, b, c;
+ int i;
+ cmsMAT3 m;
+ cmsVEC3 v, res;
+
+ if (n < 4) return 0;
+
+ for (i=0; i < n; i++) {
+
+ double xn = x[i];
+ double yn = y[i];
+
+ sum_x += xn;
+ sum_x2 += xn*xn;
+ sum_x3 += xn*xn*xn;
+ sum_x4 += xn*xn*xn*xn;
+
+ sum_y += yn;
+ sum_yx += yn*xn;
+ sum_yx2 += yn*xn*xn;
+ }
+
+ _cmsVEC3init(&m.v[0], n, sum_x, sum_x2);
+ _cmsVEC3init(&m.v[1], sum_x, sum_x2, sum_x3);
+ _cmsVEC3init(&m.v[2], sum_x2, sum_x3, sum_x4);
+
+ _cmsVEC3init(&v, sum_y, sum_yx, sum_yx2);
+
+ if (!_cmsMAT3solve(&res, &m, &v)) return 0;
+
+
+ a = res.n[2];
+ b = res.n[1];
+ c = res.n[0];
+
+ if (fabs(a) < 1.0E-10) {
+
+ return cmsmin(0, cmsmax(50, -c/b ));
+ }
+ else {
+
+ d = b*b - 4.0 * a * c;
+ if (d <= 0) {
+ return 0;
+ }
+ else {
+
+ double rt = (-b + sqrt(d)) / (2.0 * a);
+
+ return cmsmax(0, cmsmin(50, rt));
+ }
+ }
+
+}
+
+/*
+static
+cmsBool IsMonotonic(int n, const cmsFloat64Number Table[])
+{
+ int i;
+ cmsFloat64Number last;
+
+ last = Table[n-1];
+
+ for (i = n-2; i >= 0; --i) {
+
+ if (Table[i] > last)
+
+ return FALSE;
+ else
+ last = Table[i];
+
+ }
+
+ return TRUE;
+}
+*/
+
+// Calculates the black point of a destination profile.
+// This algorithm comes from the Adobe paper disclosing its black point compensation method.
+cmsBool CMSEXPORT cmsDetectDestinationBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
+{
+ cmsColorSpaceSignature ColorSpace;
+ cmsHTRANSFORM hRoundTrip = NULL;
+ cmsCIELab InitialLab, destLab, Lab;
+ cmsFloat64Number inRamp[256], outRamp[256];
+ cmsFloat64Number MinL, MaxL;
+ cmsBool NearlyStraightMidrange = TRUE;
+ cmsFloat64Number yRamp[256];
+ cmsFloat64Number x[256], y[256];
+ cmsFloat64Number lo, hi;
+ int n, l;
+ cmsProfileClassSignature devClass;
+
+ // Make sure the device class is adequate
+ devClass = cmsGetDeviceClass(hProfile);
+ if (devClass == cmsSigLinkClass ||
+ devClass == cmsSigAbstractClass ||
+ devClass == cmsSigNamedColorClass) {
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+ // Make sure intent is adequate
+ if (Intent != INTENT_PERCEPTUAL &&
+ Intent != INTENT_RELATIVE_COLORIMETRIC &&
+ Intent != INTENT_SATURATION) {
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+
+ // v4 + perceptual & saturation intents does have its own black point, and it is
+ // well specified enough to use it. Black point tag is deprecated in V4.
+ if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&
+ (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
+
+ // Matrix shaper share MRC & perceptual intents
+ if (cmsIsMatrixShaper(hProfile))
+ return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
+
+ // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
+ BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
+ BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
+ BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
+ return TRUE;
+ }
+
+
+ // Check if the profile is lut based and gray, rgb or cmyk (7.2 in Adobe's document)
+ ColorSpace = cmsGetColorSpace(hProfile);
+ if (!cmsIsCLUT(hProfile, Intent, LCMS_USED_AS_OUTPUT ) ||
+ (ColorSpace != cmsSigGrayData &&
+ ColorSpace != cmsSigRgbData &&
+ ColorSpace != cmsSigCmykData)) {
+
+ // In this case, handle as input case
+ return cmsDetectBlackPoint(BlackPoint, hProfile, Intent, dwFlags);
+ }
+
+ // It is one of the valid cases!, use Adobe algorithm
+
+
+ // Set a first guess, that should work on good profiles.
+ if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
+
+ cmsCIEXYZ IniXYZ;
+
+ // calculate initial Lab as source black point
+ if (!cmsDetectBlackPoint(&IniXYZ, hProfile, Intent, dwFlags)) {
+ return FALSE;
+ }
+
+ // convert the XYZ to lab
+ cmsXYZ2Lab(NULL, &InitialLab, &IniXYZ);
+
+ } else {
+
+ // set the initial Lab to zero, that should be the black point for perceptual and saturation
+ InitialLab.L = 0;
+ InitialLab.a = 0;
+ InitialLab.b = 0;
+ }
+
+
+ // Step 2
+ // ======
+
+ // Create a roundtrip. Define a Transform BT for all x in L*a*b*
+ hRoundTrip = CreateRoundtripXForm(hProfile, Intent);
+ if (hRoundTrip == NULL) return FALSE;
+
+ // Compute ramps
+
+ for (l=0; l < 256; l++) {
+
+ Lab.L = (cmsFloat64Number) (l * 100.0) / 255.0;
+ Lab.a = cmsmin(50, cmsmax(-50, InitialLab.a));
+ Lab.b = cmsmin(50, cmsmax(-50, InitialLab.b));
+
+ cmsDoTransform(hRoundTrip, &Lab, &destLab, 1);
+
+ inRamp[l] = Lab.L;
+ outRamp[l] = destLab.L;
+ }
+
+ // Make monotonic
+ for (l = 254; l > 0; --l) {
+ outRamp[l] = cmsmin(outRamp[l], outRamp[l+1]);
+ }
+
+ // Check
+ if (! (outRamp[0] < outRamp[255])) {
+
+ cmsDeleteTransform(hRoundTrip);
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+
+ // Test for mid range straight (only on relative colorimetric)
+
+ NearlyStraightMidrange = TRUE;
+ MinL = outRamp[0]; MaxL = outRamp[255];
+ if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
+
+ for (l=0; l < 256; l++) {
+
+ if (! ((inRamp[l] <= MinL + 0.2 * (MaxL - MinL) ) ||
+ (fabs(inRamp[l] - outRamp[l]) < 4.0 )))
+ NearlyStraightMidrange = FALSE;
+ }
+
+ // If the mid range is straight (as determined above) then the
+ // DestinationBlackPoint shall be the same as initialLab.
+ // Otherwise, the DestinationBlackPoint shall be determined
+ // using curve fitting.
+
+ if (NearlyStraightMidrange) {
+
+ cmsLab2XYZ(NULL, BlackPoint, &InitialLab);
+ cmsDeleteTransform(hRoundTrip);
+ return TRUE;
+ }
+ }
+
+
+ // curve fitting: The round-trip curve normally looks like a nearly constant section at the black point,
+ // with a corner and a nearly straight line to the white point.
+
+ for (l=0; l < 256; l++) {
+
+ yRamp[l] = (outRamp[l] - MinL) / (MaxL - MinL);
+ }
+
+ // find the black point using the least squares error quadratic curve fitting
+
+ if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
+ lo = 0.1;
+ hi = 0.5;
+ }
+ else {
+
+ // Perceptual and saturation
+ lo = 0.03;
+ hi = 0.25;
+ }
+
+ // Capture shadow points for the fitting.
+ n = 0;
+ for (l=0; l < 256; l++) {
+
+ cmsFloat64Number ff = yRamp[l];
+
+ if (ff >= lo && ff < hi) {
+ x[n] = inRamp[l];
+ y[n] = yRamp[l];
+ n++;
+ }
+ }
+
+
+ // No suitable points
+ if (n < 3 ) {
+ cmsDeleteTransform(hRoundTrip);
+ BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
+ return FALSE;
+ }
+
+
+ // fit and get the vertex of quadratic curve
+ Lab.L = RootOfLeastSquaresFitQuadraticCurve(n, x, y);
+
+ if (Lab.L < 0.0) { // clip to zero L* if the vertex is negative
+ Lab.L = 0;
+ }
+
+ Lab.a = InitialLab.a;
+ Lab.b = InitialLab.b;
+
+ cmsLab2XYZ(NULL, BlackPoint, &Lab);
+
+ cmsDeleteTransform(hRoundTrip);
+ return TRUE;
+}
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