1 //---------------------------------------------------------------------------------
3 // Little Color Management System
4 // Copyright (c) 1998-2016 Marti Maria Saguer
6 // Permission is hereby granted, free of charge, to any person obtaining
7 // a copy of this software and associated documentation files (the "Software"),
8 // to deal in the Software without restriction, including without limitation
9 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 // and/or sell copies of the Software, and to permit persons to whom the Software
11 // is furnished to do so, subject to the following conditions:
13 // The above copyright notice and this permission notice shall be included in
14 // all copies or substantial portions of the Software.
16 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
17 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
18 // THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
19 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
20 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
21 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
22 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24 //---------------------------------------------------------------------------------
27 #include "lcms2_internal.h"
30 #define cmsmin(a, b) (((a) < (b)) ? (a) : (b))
31 #define cmsmax(a, b) (((a) > (b)) ? (a) : (b))
33 // This file contains routines for resampling and LUT optimization, black point detection
34 // and black preservation.
36 // Black point detection -------------------------------------------------------------------------
39 // PCS -> PCS round trip transform, always uses relative intent on the device -> pcs
41 cmsHTRANSFORM CreateRoundtripXForm(cmsHPROFILE hProfile, cmsUInt32Number nIntent)
43 cmsContext ContextID = cmsGetProfileContextID(hProfile);
44 cmsHPROFILE hLab = cmsCreateLab4ProfileTHR(ContextID, NULL);
46 cmsBool BPC[4] = { FALSE, FALSE, FALSE, FALSE };
47 cmsFloat64Number States[4] = { 1.0, 1.0, 1.0, 1.0 };
48 cmsHPROFILE hProfiles[4];
49 cmsUInt32Number Intents[4];
51 hProfiles[0] = hLab; hProfiles[1] = hProfile; hProfiles[2] = hProfile; hProfiles[3] = hLab;
52 Intents[0] = INTENT_RELATIVE_COLORIMETRIC; Intents[1] = nIntent; Intents[2] = INTENT_RELATIVE_COLORIMETRIC; Intents[3] = INTENT_RELATIVE_COLORIMETRIC;
54 xform = cmsCreateExtendedTransform(ContextID, 4, hProfiles, BPC, Intents,
55 States, NULL, 0, TYPE_Lab_DBL, TYPE_Lab_DBL, cmsFLAGS_NOCACHE|cmsFLAGS_NOOPTIMIZE);
57 cmsCloseProfile(hLab);
61 // Use darker colorants to obtain black point. This works in the relative colorimetric intent and
62 // assumes more ink results in darker colors. No ink limit is assumed.
64 cmsBool BlackPointAsDarkerColorant(cmsHPROFILE hInput,
65 cmsUInt32Number Intent,
66 cmsCIEXYZ* BlackPoint,
67 cmsUInt32Number dwFlags)
69 cmsUInt16Number *Black;
71 cmsColorSpaceSignature Space;
72 cmsUInt32Number nChannels;
73 cmsUInt32Number dwFormat;
77 cmsContext ContextID = cmsGetProfileContextID(hInput);
79 // If the profile does not support input direction, assume Black point 0
80 if (!cmsIsIntentSupported(hInput, Intent, LCMS_USED_AS_INPUT)) {
82 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
86 // Create a formatter which has n channels and floating point
87 dwFormat = cmsFormatterForColorspaceOfProfile(hInput, 2, FALSE);
89 // Try to get black by using black colorant
90 Space = cmsGetColorSpace(hInput);
92 // This function returns darker colorant in 16 bits for several spaces
93 if (!_cmsEndPointsBySpace(Space, NULL, &Black, &nChannels)) {
95 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
99 if (nChannels != T_CHANNELS(dwFormat)) {
100 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
104 // Lab will be used as the output space, but lab2 will avoid recursion
105 hLab = cmsCreateLab2ProfileTHR(ContextID, NULL);
107 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
111 // Create the transform
112 xform = cmsCreateTransformTHR(ContextID, hInput, dwFormat,
113 hLab, TYPE_Lab_DBL, Intent, cmsFLAGS_NOOPTIMIZE|cmsFLAGS_NOCACHE);
114 cmsCloseProfile(hLab);
118 // Something went wrong. Get rid of open resources and return zero as black
119 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
123 // Convert black to Lab
124 cmsDoTransform(xform, Black, &Lab, 1);
126 // Force it to be neutral, clip to max. L* of 50
128 if (Lab.L > 50) Lab.L = 50;
130 // Free the resources
131 cmsDeleteTransform(xform);
133 // Convert from Lab (which is now clipped) to XYZ.
134 cmsLab2XYZ(NULL, &BlackXYZ, &Lab);
136 if (BlackPoint != NULL)
137 *BlackPoint = BlackXYZ;
141 cmsUNUSED_PARAMETER(dwFlags);
144 // Get a black point of output CMYK profile, discounting any ink-limiting embedded
145 // in the profile. For doing that, we use perceptual intent in input direction:
146 // Lab (0, 0, 0) -> [Perceptual] Profile -> CMYK -> [Rel. colorimetric] Profile -> Lab
148 cmsBool BlackPointUsingPerceptualBlack(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile)
150 cmsHTRANSFORM hRoundTrip;
151 cmsCIELab LabIn, LabOut;
154 // Is the intent supported by the profile?
155 if (!cmsIsIntentSupported(hProfile, INTENT_PERCEPTUAL, LCMS_USED_AS_INPUT)) {
157 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
161 hRoundTrip = CreateRoundtripXForm(hProfile, INTENT_PERCEPTUAL);
162 if (hRoundTrip == NULL) {
163 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
167 LabIn.L = LabIn.a = LabIn.b = 0;
168 cmsDoTransform(hRoundTrip, &LabIn, &LabOut, 1);
170 // Clip Lab to reasonable limits
171 if (LabOut.L > 50) LabOut.L = 50;
172 LabOut.a = LabOut.b = 0;
174 cmsDeleteTransform(hRoundTrip);
177 cmsLab2XYZ(NULL, &BlackXYZ, &LabOut);
179 if (BlackPoint != NULL)
180 *BlackPoint = BlackXYZ;
185 // This function shouldn't exist at all -- there is such quantity of broken
186 // profiles on black point tag, that we must somehow fix chromaticity to
187 // avoid huge tint when doing Black point compensation. This function does
188 // just that. There is a special flag for using black point tag, but turned
189 // off by default because it is bogus on most profiles. The detection algorithm
190 // involves to turn BP to neutral and to use only L component.
191 cmsBool CMSEXPORT cmsDetectBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
193 cmsProfileClassSignature devClass;
195 // Make sure the device class is adequate
196 devClass = cmsGetDeviceClass(hProfile);
197 if (devClass == cmsSigLinkClass ||
198 devClass == cmsSigAbstractClass ||
199 devClass == cmsSigNamedColorClass) {
200 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
204 // Make sure intent is adequate
205 if (Intent != INTENT_PERCEPTUAL &&
206 Intent != INTENT_RELATIVE_COLORIMETRIC &&
207 Intent != INTENT_SATURATION) {
208 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
212 // v4 + perceptual & saturation intents does have its own black point, and it is
213 // well specified enough to use it. Black point tag is deprecated in V4.
214 if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&
215 (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
217 // Matrix shaper share MRC & perceptual intents
218 if (cmsIsMatrixShaper(hProfile))
219 return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
221 // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
222 BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
223 BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
224 BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
230 #ifdef CMS_USE_PROFILE_BLACK_POINT_TAG
232 // v2, v4 rel/abs colorimetric
233 if (cmsIsTag(hProfile, cmsSigMediaBlackPointTag) &&
234 Intent == INTENT_RELATIVE_COLORIMETRIC) {
236 cmsCIEXYZ *BlackPtr, BlackXYZ, UntrustedBlackPoint, TrustedBlackPoint, MediaWhite;
239 // If black point is specified, then use it,
241 BlackPtr = cmsReadTag(hProfile, cmsSigMediaBlackPointTag);
242 if (BlackPtr != NULL) {
244 BlackXYZ = *BlackPtr;
245 _cmsReadMediaWhitePoint(&MediaWhite, hProfile);
247 // Black point is absolute XYZ, so adapt to D50 to get PCS value
248 cmsAdaptToIlluminant(&UntrustedBlackPoint, &MediaWhite, cmsD50_XYZ(), &BlackXYZ);
250 // Force a=b=0 to get rid of any chroma
251 cmsXYZ2Lab(NULL, &Lab, &UntrustedBlackPoint);
253 if (Lab.L > 50) Lab.L = 50; // Clip to L* <= 50
254 cmsLab2XYZ(NULL, &TrustedBlackPoint, &Lab);
256 if (BlackPoint != NULL)
257 *BlackPoint = TrustedBlackPoint;
264 // That is about v2 profiles.
266 // If output profile, discount ink-limiting and that's all
267 if (Intent == INTENT_RELATIVE_COLORIMETRIC &&
268 (cmsGetDeviceClass(hProfile) == cmsSigOutputClass) &&
269 (cmsGetColorSpace(hProfile) == cmsSigCmykData))
270 return BlackPointUsingPerceptualBlack(BlackPoint, hProfile);
272 // Nope, compute BP using current intent.
273 return BlackPointAsDarkerColorant(hProfile, Intent, BlackPoint, dwFlags);
278 // ---------------------------------------------------------------------------------------------------------
280 // Least Squares Fit of a Quadratic Curve to Data
281 // http://www.personal.psu.edu/jhm/f90/lectures/lsq2.html
284 cmsFloat64Number RootOfLeastSquaresFitQuadraticCurve(int n, cmsFloat64Number x[], cmsFloat64Number y[])
286 double sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0;
287 double sum_y = 0, sum_yx = 0, sum_yx2 = 0;
295 for (i=0; i < n; i++) {
303 sum_x4 += xn*xn*xn*xn;
310 _cmsVEC3init(&m.v[0], n, sum_x, sum_x2);
311 _cmsVEC3init(&m.v[1], sum_x, sum_x2, sum_x3);
312 _cmsVEC3init(&m.v[2], sum_x2, sum_x3, sum_x4);
314 _cmsVEC3init(&v, sum_y, sum_yx, sum_yx2);
316 if (!_cmsMAT3solve(&res, &m, &v)) return 0;
323 if (fabs(a) < 1.0E-10) {
325 return cmsmin(0, cmsmax(50, -c/b ));
329 d = b*b - 4.0 * a * c;
335 double rt = (-b + sqrt(d)) / (2.0 * a);
337 return cmsmax(0, cmsmin(50, rt));
345 // Calculates the black point of a destination profile.
346 // This algorithm comes from the Adobe paper disclosing its black point compensation method.
347 cmsBool CMSEXPORT cmsDetectDestinationBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
349 cmsColorSpaceSignature ColorSpace;
350 cmsHTRANSFORM hRoundTrip = NULL;
351 cmsCIELab InitialLab, destLab, Lab;
352 cmsFloat64Number inRamp[256], outRamp[256];
353 cmsFloat64Number MinL, MaxL;
354 cmsBool NearlyStraightMidrange = TRUE;
355 cmsFloat64Number yRamp[256];
356 cmsFloat64Number x[256], y[256];
357 cmsFloat64Number lo, hi;
359 cmsProfileClassSignature devClass;
361 // Make sure the device class is adequate
362 devClass = cmsGetDeviceClass(hProfile);
363 if (devClass == cmsSigLinkClass ||
364 devClass == cmsSigAbstractClass ||
365 devClass == cmsSigNamedColorClass) {
366 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
370 // Make sure intent is adequate
371 if (Intent != INTENT_PERCEPTUAL &&
372 Intent != INTENT_RELATIVE_COLORIMETRIC &&
373 Intent != INTENT_SATURATION) {
374 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
379 // v4 + perceptual & saturation intents does have its own black point, and it is
380 // well specified enough to use it. Black point tag is deprecated in V4.
381 if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&
382 (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
384 // Matrix shaper share MRC & perceptual intents
385 if (cmsIsMatrixShaper(hProfile))
386 return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
388 // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
389 BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
390 BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
391 BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
396 // Check if the profile is lut based and gray, rgb or cmyk (7.2 in Adobe's document)
397 ColorSpace = cmsGetColorSpace(hProfile);
398 if (!cmsIsCLUT(hProfile, Intent, LCMS_USED_AS_OUTPUT ) ||
399 (ColorSpace != cmsSigGrayData &&
400 ColorSpace != cmsSigRgbData &&
401 ColorSpace != cmsSigCmykData)) {
403 // In this case, handle as input case
404 return cmsDetectBlackPoint(BlackPoint, hProfile, Intent, dwFlags);
407 // It is one of the valid cases!, use Adobe algorithm
410 // Set a first guess, that should work on good profiles.
411 if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
415 // calculate initial Lab as source black point
416 if (!cmsDetectBlackPoint(&IniXYZ, hProfile, Intent, dwFlags)) {
420 // convert the XYZ to lab
421 cmsXYZ2Lab(NULL, &InitialLab, &IniXYZ);
425 // set the initial Lab to zero, that should be the black point for perceptual and saturation
435 // Create a roundtrip. Define a Transform BT for all x in L*a*b*
436 hRoundTrip = CreateRoundtripXForm(hProfile, Intent);
437 if (hRoundTrip == NULL) return FALSE;
441 for (l=0; l < 256; l++) {
443 Lab.L = (cmsFloat64Number) (l * 100.0) / 255.0;
444 Lab.a = cmsmin(50, cmsmax(-50, InitialLab.a));
445 Lab.b = cmsmin(50, cmsmax(-50, InitialLab.b));
447 cmsDoTransform(hRoundTrip, &Lab, &destLab, 1);
450 outRamp[l] = destLab.L;
454 for (l = 254; l > 0; --l) {
455 outRamp[l] = cmsmin(outRamp[l], outRamp[l+1]);
459 if (! (outRamp[0] < outRamp[255])) {
461 cmsDeleteTransform(hRoundTrip);
462 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
467 // Test for mid range straight (only on relative colorimetric)
468 NearlyStraightMidrange = TRUE;
469 MinL = outRamp[0]; MaxL = outRamp[255];
470 if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
472 for (l=0; l < 256; l++) {
474 if (! ((inRamp[l] <= MinL + 0.2 * (MaxL - MinL) ) ||
475 (fabs(inRamp[l] - outRamp[l]) < 4.0 )))
476 NearlyStraightMidrange = FALSE;
479 // If the mid range is straight (as determined above) then the
480 // DestinationBlackPoint shall be the same as initialLab.
481 // Otherwise, the DestinationBlackPoint shall be determined
482 // using curve fitting.
483 if (NearlyStraightMidrange) {
485 cmsLab2XYZ(NULL, BlackPoint, &InitialLab);
486 cmsDeleteTransform(hRoundTrip);
492 // curve fitting: The round-trip curve normally looks like a nearly constant section at the black point,
493 // with a corner and a nearly straight line to the white point.
494 for (l=0; l < 256; l++) {
496 yRamp[l] = (outRamp[l] - MinL) / (MaxL - MinL);
499 // find the black point using the least squares error quadratic curve fitting
500 if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
506 // Perceptual and saturation
511 // Capture shadow points for the fitting.
513 for (l=0; l < 256; l++) {
515 cmsFloat64Number ff = yRamp[l];
517 if (ff >= lo && ff < hi) {
525 // No suitable points
527 cmsDeleteTransform(hRoundTrip);
528 BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
533 // fit and get the vertex of quadratic curve
534 Lab.L = RootOfLeastSquaresFitQuadraticCurve(n, x, y);
536 if (Lab.L < 0.0) { // clip to zero L* if the vertex is negative
540 Lab.a = InitialLab.a;
541 Lab.b = InitialLab.b;
543 cmsLab2XYZ(NULL, BlackPoint, &Lab);
545 cmsDeleteTransform(hRoundTrip);