static int WriteInputMatrixShaper(cmsIOHANDLER* m, cmsHPROFILE hProfile, cmsStage* Matrix, cmsStage* Shaper) { cmsColorSpaceSignature ColorSpace; int rc; cmsCIEXYZ BlackPointAdaptedToD50; ColorSpace = cmsGetColorSpace(hProfile); cmsDetectBlackPoint(&BlackPointAdaptedToD50, hProfile, INTENT_RELATIVE_COLORIMETRIC, 0); if (ColorSpace == cmsSigGrayData) { cmsToneCurve** ShaperCurve = _cmsStageGetPtrToCurveSet(Shaper); rc = EmitCIEBasedA(m, ShaperCurve[0], &BlackPointAdaptedToD50); } else if (ColorSpace == cmsSigRgbData) { rc = EmitCIEBasedABC(m, GetPtrToMatrix(Matrix), _cmsStageGetPtrToCurveSet(Shaper), &BlackPointAdaptedToD50); } else { cmsSignalError(m ->ContextID, cmsERROR_COLORSPACE_CHECK, "Profile is not suitable for CSA. Unsupported colorspace."); return 0; } return rc; }
static int WriteInputMatrixShaper(cmsIOHANDLER* m, cmsHPROFILE hProfile, cmsStage* Matrix, cmsStage* Shaper) { cmsColorSpaceSignature ColorSpace; int rc; cmsCIEXYZ BlackPointAdaptedToD50; ColorSpace = cmsGetColorSpace(hProfile); cmsDetectBlackPoint(&BlackPointAdaptedToD50, hProfile, INTENT_RELATIVE_COLORIMETRIC, 0); if (ColorSpace == cmsSigGrayData) { cmsToneCurve** ShaperCurve = _cmsStageGetPtrToCurveSet(Shaper); rc = EmitCIEBasedA(m, ShaperCurve[0], &BlackPointAdaptedToD50); } else if (ColorSpace == cmsSigRgbData) { cmsMAT3 Mat; int i, j; memmove(&Mat, GetPtrToMatrix(Matrix), sizeof(Mat)); for (i=0; i < 3; i++) for (j=0; j < 3; j++) Mat.v[i].n[j] *= MAX_ENCODEABLE_XYZ; rc = EmitCIEBasedABC(m, (cmsFloat64Number *) &Mat, _cmsStageGetPtrToCurveSet(Shaper), &BlackPointAdaptedToD50); } else { cmsSignalError(m ->ContextID, cmsERROR_COLORSPACE_CHECK, "Profile is not suitable for CSA. Unsupported colorspace."); return 0; } return rc; }
static int WriteInputLUT(cmsIOHANDLER* m, cmsHPROFILE hProfile, int Intent, cmsUInt32Number dwFlags) { cmsHPROFILE hLab; cmsHTRANSFORM xform; cmsUInt32Number nChannels; cmsUInt32Number InputFormat; int rc; cmsHPROFILE Profiles[2]; cmsCIEXYZ BlackPointAdaptedToD50; // Does create a device-link based transform. // The DeviceLink is next dumped as working CSA. InputFormat = cmsFormatterForColorspaceOfProfile(hProfile, 2, FALSE); nChannels = T_CHANNELS(InputFormat); cmsDetectBlackPoint(&BlackPointAdaptedToD50, hProfile, Intent, 0); // Adjust output to Lab4 hLab = cmsCreateLab4ProfileTHR(m ->ContextID, NULL); Profiles[0] = hProfile; Profiles[1] = hLab; xform = cmsCreateMultiprofileTransform(Profiles, 2, InputFormat, TYPE_Lab_DBL, Intent, 0); cmsCloseProfile(hLab); if (xform == NULL) { cmsSignalError(m ->ContextID, cmsERROR_COLORSPACE_CHECK, "Cannot create transform Profile -> Lab"); return 0; } // Only 1, 3 and 4 channels are allowed switch (nChannels) { case 1: { cmsToneCurve* Gray2Y = ExtractGray2Y(m ->ContextID, hProfile, Intent); EmitCIEBasedA(m, Gray2Y, &BlackPointAdaptedToD50); cmsFreeToneCurve(Gray2Y); } break; case 3: case 4: { cmsUInt32Number OutFrm = TYPE_Lab_16; cmsPipeline* DeviceLink; _cmsTRANSFORM* v = (_cmsTRANSFORM*) xform; DeviceLink = cmsPipelineDup(v ->Lut); if (DeviceLink == NULL) return 0; dwFlags |= cmsFLAGS_FORCE_CLUT; _cmsOptimizePipeline(&DeviceLink, Intent, &InputFormat, &OutFrm, &dwFlags); rc = EmitCIEBasedDEF(m, DeviceLink, Intent, &BlackPointAdaptedToD50); cmsPipelineFree(DeviceLink); } break; default: cmsSignalError(m ->ContextID, cmsERROR_COLORSPACE_CHECK, "Only 3, 4 channels supported for CSA. This profile has %d channels.", nChannels); return 0; } cmsDeleteTransform(xform); return 1; }
static int WriteOutputLUT(cmsIOHANDLER* m, cmsHPROFILE hProfile, int Intent, cmsUInt32Number dwFlags) { cmsHPROFILE hLab; cmsHTRANSFORM xform; int i, nChannels; cmsUInt32Number OutputFormat; _cmsTRANSFORM* v; cmsPipeline* DeviceLink; cmsHPROFILE Profiles[3]; cmsCIEXYZ BlackPointAdaptedToD50; cmsBool lDoBPC = (dwFlags & cmsFLAGS_BLACKPOINTCOMPENSATION); cmsBool lFixWhite = !(dwFlags & cmsFLAGS_NOWHITEONWHITEFIXUP); cmsUInt32Number InFrm = TYPE_Lab_16; int RelativeEncodingIntent; cmsColorSpaceSignature ColorSpace; hLab = cmsCreateLab4ProfileTHR(m ->ContextID, NULL); if (hLab == NULL) return 0; OutputFormat = cmsFormatterForColorspaceOfProfile(hProfile, 2, FALSE); nChannels = T_CHANNELS(OutputFormat); ColorSpace = cmsGetColorSpace(hProfile); // For absolute colorimetric, the LUT is encoded as relative in order to preserve precision. RelativeEncodingIntent = Intent; if (RelativeEncodingIntent == INTENT_ABSOLUTE_COLORIMETRIC) RelativeEncodingIntent = INTENT_RELATIVE_COLORIMETRIC; // Use V4 Lab always Profiles[0] = hLab; Profiles[1] = hProfile; xform = cmsCreateMultiprofileTransformTHR(m ->ContextID, Profiles, 2, TYPE_Lab_DBL, OutputFormat, RelativeEncodingIntent, 0); cmsCloseProfile(hLab); if (xform == NULL) { cmsSignalError(m ->ContextID, cmsERROR_COLORSPACE_CHECK, "Cannot create transform Lab -> Profile in CRD creation"); return 0; } // Get a copy of the internal devicelink v = (_cmsTRANSFORM*) xform; DeviceLink = cmsPipelineDup(v ->Lut); if (DeviceLink == NULL) return 0; // We need a CLUT dwFlags |= cmsFLAGS_FORCE_CLUT; _cmsOptimizePipeline(&DeviceLink, RelativeEncodingIntent, &InFrm, &OutputFormat, &dwFlags); _cmsIOPrintf(m, "<<\n"); _cmsIOPrintf(m, "/ColorRenderingType 1\n"); cmsDetectBlackPoint(&BlackPointAdaptedToD50, hProfile, Intent, 0); // Emit headers, etc. EmitWhiteBlackD50(m, &BlackPointAdaptedToD50); EmitPQRStage(m, hProfile, lDoBPC, Intent == INTENT_ABSOLUTE_COLORIMETRIC); EmitXYZ2Lab(m); // FIXUP: map Lab (100, 0, 0) to perfect white, because the particular encoding for Lab // does map a=b=0 not falling into any specific node. Since range a,b goes -128..127, // zero is slightly moved towards right, so assure next node (in L=100 slice) is mapped to // zero. This would sacrifice a bit of highlights, but failure to do so would cause // scum dot. Ouch. if (Intent == INTENT_ABSOLUTE_COLORIMETRIC) lFixWhite = FALSE; _cmsIOPrintf(m, "/RenderTable "); WriteCLUT(m, cmsPipelineGetPtrToFirstStage(DeviceLink), "<", ">\n", "", "", lFixWhite, ColorSpace); _cmsIOPrintf(m, " %d {} bind ", nChannels); for (i=1; i < nChannels; i++) _cmsIOPrintf(m, "dup "); _cmsIOPrintf(m, "]\n"); EmitIntent(m, Intent); _cmsIOPrintf(m, ">>\n"); if (!(dwFlags & cmsFLAGS_NODEFAULTRESOURCEDEF)) { _cmsIOPrintf(m, "/Current exch /ColorRendering defineresource pop\n"); } cmsPipelineFree(DeviceLink); cmsDeleteTransform(xform); return 1; }
// Compute the conversion layer static cmsBool ComputeConversion(int i, cmsHPROFILE hProfiles[], cmsUInt32Number Intent, cmsBool BPC, cmsFloat64Number AdaptationState, cmsMAT3* m, cmsVEC3* off) { int k; // m and off are set to identity and this is detected latter on _cmsMAT3identity(m); _cmsVEC3init(off, 0, 0, 0); // If intent is abs. colorimetric, if (Intent == INTENT_ABSOLUTE_COLORIMETRIC) { cmsCIEXYZ WhitePointIn, WhitePointOut; cmsMAT3 ChromaticAdaptationMatrixIn, ChromaticAdaptationMatrixOut; _cmsReadMediaWhitePoint(&WhitePointIn, hProfiles[i-1]); _cmsReadCHAD(&ChromaticAdaptationMatrixIn, hProfiles[i-1]); _cmsReadMediaWhitePoint(&WhitePointOut, hProfiles[i]); _cmsReadCHAD(&ChromaticAdaptationMatrixOut, hProfiles[i]); if (!ComputeAbsoluteIntent(AdaptationState, &WhitePointIn, &ChromaticAdaptationMatrixIn, &WhitePointOut, &ChromaticAdaptationMatrixOut, m)) return FALSE; } else { // Rest of intents may apply BPC. if (BPC) { cmsCIEXYZ BlackPointIn, BlackPointOut; cmsDetectBlackPoint(&BlackPointIn, hProfiles[i-1], Intent, 0); cmsDetectDestinationBlackPoint(&BlackPointOut, hProfiles[i], Intent, 0); // If black points are equal, then do nothing if (BlackPointIn.X != BlackPointOut.X || BlackPointIn.Y != BlackPointOut.Y || BlackPointIn.Z != BlackPointOut.Z) ComputeBlackPointCompensation(&BlackPointIn, &BlackPointOut, m, off); } } // Offset should be adjusted because the encoding. We encode XYZ normalized to 0..1.0, // to do that, we divide by MAX_ENCODEABLE_XZY. The conversion stage goes XYZ -> XYZ so // we have first to convert from encoded to XYZ and then convert back to encoded. // y = Mx + Off // x = x'c // y = M x'c + Off // y = y'c; y' = y / c // y' = (Mx'c + Off) /c = Mx' + (Off / c) for (k=0; k < 3; k++) { off ->n[k] /= MAX_ENCODEABLE_XYZ; } 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; }
// 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 MinL, MaxL; cmsBool NearlyStraightMidRange = FALSE; cmsFloat64Number L; cmsFloat64Number x[101], y[101]; cmsFloat64Number lo, hi, NonMonoMin; int n, l, i, NonMonoIndx; // 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!, presto chargo hocus pocus, go for the Adobe magic // Step 1 // ====== // 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; // Calculate Min L* Lab = InitialLab; Lab.L = 0; cmsDoTransform(hRoundTrip, &Lab, &destLab, 1); MinL = destLab.L; // Calculate Max L* Lab = InitialLab; Lab.L = 100; cmsDoTransform(hRoundTrip, &Lab, &destLab, 1); MaxL = destLab.L; // Step 3 // ====== // check if quadratic estimation needs to be done. if (Intent == INTENT_RELATIVE_COLORIMETRIC) { // Conceptually, this code tests how close the source l and converted L are to one another in the mid-range // of the values. If the converted ramp of L values is close enough to a straight line y=x, then InitialLab // is good enough to be the DestinationBlackPoint, NearlyStraightMidRange = TRUE; for (l=0; l <= 100; l++) { Lab.L = l; Lab.a = InitialLab.a; Lab.b = InitialLab.b; cmsDoTransform(hRoundTrip, &Lab, &destLab, 1); L = destLab.L; // Check the mid range in 20% after MinL if (L > (MinL + 0.2 * (MaxL - MinL))) { // Is close enough? if (fabs(L - l) > 4.0) { // Too far away, profile is buggy! NearlyStraightMidRange = FALSE; break; } } } } else { // Check is always performed for perceptual and saturation intents NearlyStraightMidRange = FALSE; } // If no furter checking is needed, we are done if (NearlyStraightMidRange) { cmsLab2XYZ(NULL, BlackPoint, &InitialLab); cmsDeleteTransform(hRoundTrip); return TRUE; } // 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. // STEP 4 // ======= // 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 points for the fitting. n = 0; for (l=0; l <= 100; l++) { cmsFloat64Number ff; Lab.L = (cmsFloat64Number) l; Lab.a = InitialLab.a; Lab.b = InitialLab.b; cmsDoTransform(hRoundTrip, &Lab, &destLab, 1); ff = (destLab.L - MinL)/(MaxL - MinL); if (ff >= lo && ff < hi) { x[n] = Lab.L; y[n] = ff; n++; } } // This part is not on the Adobe paper, but I found is necessary for getting any result. if (IsMonotonic(n, y)) { // Monotonic means lower point is stil valid cmsLab2XYZ(NULL, BlackPoint, &InitialLab); cmsDeleteTransform(hRoundTrip); return TRUE; } // No suitable points, regret and use safer algorithm if (n == 0) { cmsDeleteTransform(hRoundTrip); return cmsDetectBlackPoint(BlackPoint, hProfile, Intent, dwFlags); } NonMonoMin = 100; NonMonoIndx = 0; for (i=0; i < n; i++) { if (y[i] < NonMonoMin) { NonMonoIndx = i; NonMonoMin = y[i]; } } Lab.L = x[NonMonoIndx]; // fit and get the vertex of quadratic curve Lab.L = VertexOfLeastSquaresFitQuadraticCurve(n, x, y); if (Lab.L < 0.0 || Lab.L > 50.0) { // 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; }