/src/mupdf/thirdparty/lcms2/src/cmssamp.c
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1 | | //--------------------------------------------------------------------------------- |
2 | | // |
3 | | // Little Color Management System |
4 | | // Copyright (c) 1998-2022 Marti Maria Saguer |
5 | | // |
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: |
12 | | // |
13 | | // The above copyright notice and this permission notice shall be included in |
14 | | // all copies or substantial portions of the Software. |
15 | | // |
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. |
23 | | // |
24 | | //--------------------------------------------------------------------------------- |
25 | | // |
26 | | |
27 | | #include "lcms2_internal.h" |
28 | | |
29 | | |
30 | 37.8k | #define cmsmin(a, b) (((a) < (b)) ? (a) : (b)) |
31 | 34 | #define cmsmax(a, b) (((a) > (b)) ? (a) : (b)) |
32 | | |
33 | | // This file contains routines for resampling and LUT optimization, black point detection |
34 | | // and black preservation. |
35 | | |
36 | | // Black point detection ------------------------------------------------------------------------- |
37 | | |
38 | | |
39 | | // PCS -> PCS round trip transform, always uses relative intent on the device -> pcs |
40 | | static |
41 | | cmsHTRANSFORM CreateRoundtripXForm(cmsContext ContextID, cmsHPROFILE hProfile, cmsUInt32Number nIntent) |
42 | 927 | { |
43 | 927 | cmsHPROFILE hLab = cmsCreateLab4Profile(ContextID, NULL); |
44 | 927 | cmsHTRANSFORM xform; |
45 | 927 | cmsBool BPC[4] = { FALSE, FALSE, FALSE, FALSE }; |
46 | 927 | cmsFloat64Number States[4] = { 1.0, 1.0, 1.0, 1.0 }; |
47 | 927 | cmsHPROFILE hProfiles[4]; |
48 | 927 | cmsUInt32Number Intents[4]; |
49 | | |
50 | 927 | hProfiles[0] = hLab; hProfiles[1] = hProfile; hProfiles[2] = hProfile; hProfiles[3] = hLab; |
51 | 927 | Intents[0] = INTENT_RELATIVE_COLORIMETRIC; Intents[1] = nIntent; Intents[2] = INTENT_RELATIVE_COLORIMETRIC; Intents[3] = INTENT_RELATIVE_COLORIMETRIC; |
52 | | |
53 | 927 | xform = cmsCreateExtendedTransform(ContextID, 4, hProfiles, BPC, Intents, |
54 | 927 | States, NULL, 0, TYPE_Lab_DBL, TYPE_Lab_DBL, cmsFLAGS_NOCACHE|cmsFLAGS_NOOPTIMIZE); |
55 | | |
56 | 927 | cmsCloseProfile(ContextID, hLab); |
57 | 927 | return xform; |
58 | 927 | } |
59 | | |
60 | | // Use darker colorants to obtain black point. This works in the relative colorimetric intent and |
61 | | // assumes more ink results in darker colors. No ink limit is assumed. |
62 | | static |
63 | | cmsBool BlackPointAsDarkerColorant(cmsContext ContextID, |
64 | | cmsHPROFILE hInput, |
65 | | cmsUInt32Number Intent, |
66 | | cmsCIEXYZ* BlackPoint, |
67 | | cmsUInt32Number dwFlags) |
68 | 15.9k | { |
69 | 15.9k | cmsUInt16Number *Black; |
70 | 15.9k | cmsHTRANSFORM xform; |
71 | 15.9k | cmsColorSpaceSignature Space; |
72 | 15.9k | cmsUInt32Number nChannels; |
73 | 15.9k | cmsUInt32Number dwFormat; |
74 | 15.9k | cmsHPROFILE hLab; |
75 | 15.9k | cmsCIELab Lab; |
76 | 15.9k | cmsCIEXYZ BlackXYZ; |
77 | | |
78 | | // If the profile does not support input direction, assume Black point 0 |
79 | 15.9k | if (!cmsIsIntentSupported(ContextID, hInput, Intent, LCMS_USED_AS_INPUT)) { |
80 | | |
81 | 43 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
82 | 43 | return FALSE; |
83 | 43 | } |
84 | | |
85 | | // Create a formatter which has n channels and no floating point |
86 | 15.8k | dwFormat = cmsFormatterForColorspaceOfProfile(ContextID, hInput, 2, FALSE); |
87 | | |
88 | | // Try to get black by using black colorant |
89 | 15.8k | Space = cmsGetColorSpace(ContextID, hInput); |
90 | | |
91 | | // This function returns darker colorant in 16 bits for several spaces |
92 | 15.8k | if (!_cmsEndPointsBySpace(Space, NULL, &Black, &nChannels)) { |
93 | |
|
94 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
95 | 0 | return FALSE; |
96 | 0 | } |
97 | | |
98 | 15.8k | if (nChannels != T_CHANNELS(dwFormat)) { |
99 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
100 | 0 | return FALSE; |
101 | 0 | } |
102 | | |
103 | | // Lab will be used as the output space, but lab2 will avoid recursion |
104 | 15.8k | hLab = cmsCreateLab2Profile(ContextID, NULL); |
105 | 15.8k | if (hLab == NULL) { |
106 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
107 | 0 | return FALSE; |
108 | 0 | } |
109 | | |
110 | | // Create the transform |
111 | 15.8k | xform = cmsCreateTransform(ContextID, hInput, dwFormat, |
112 | 15.8k | hLab, TYPE_Lab_DBL, Intent, cmsFLAGS_NOOPTIMIZE|cmsFLAGS_NOCACHE); |
113 | 15.8k | cmsCloseProfile(ContextID, hLab); |
114 | | |
115 | 15.8k | if (xform == NULL) { |
116 | | |
117 | | // Something went wrong. Get rid of open resources and return zero as black |
118 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
119 | 0 | return FALSE; |
120 | 0 | } |
121 | | |
122 | | // Convert black to Lab |
123 | 15.8k | cmsDoTransform(ContextID, xform, Black, &Lab, 1); |
124 | | |
125 | | // Force it to be neutral, clip to max. L* of 50 |
126 | 15.8k | Lab.a = Lab.b = 0; |
127 | 15.8k | if (Lab.L > 50) Lab.L = 50; |
128 | 15.8k | if (Lab.L < 0) Lab.L = 0; |
129 | | |
130 | | // Free the resources |
131 | 15.8k | cmsDeleteTransform(ContextID, xform); |
132 | | |
133 | | // Convert from Lab (which is now clipped) to XYZ. |
134 | 15.8k | cmsLab2XYZ(ContextID, NULL, &BlackXYZ, &Lab); |
135 | | |
136 | 15.8k | if (BlackPoint != NULL) |
137 | 15.8k | *BlackPoint = BlackXYZ; |
138 | | |
139 | 15.8k | return TRUE; |
140 | | |
141 | 0 | cmsUNUSED_PARAMETER(dwFlags); |
142 | 0 | } |
143 | | |
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 |
147 | | static |
148 | | cmsBool BlackPointUsingPerceptualBlack(cmsContext ContextID, cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile) |
149 | 890 | { |
150 | 890 | cmsHTRANSFORM hRoundTrip; |
151 | 890 | cmsCIELab LabIn, LabOut; |
152 | 890 | cmsCIEXYZ BlackXYZ; |
153 | | |
154 | | // Is the intent supported by the profile? |
155 | 890 | if (!cmsIsIntentSupported(ContextID, hProfile, INTENT_PERCEPTUAL, LCMS_USED_AS_INPUT)) { |
156 | |
|
157 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
158 | 0 | return TRUE; |
159 | 0 | } |
160 | | |
161 | 890 | hRoundTrip = CreateRoundtripXForm(ContextID, hProfile, INTENT_PERCEPTUAL); |
162 | 890 | if (hRoundTrip == NULL) { |
163 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
164 | 0 | return FALSE; |
165 | 0 | } |
166 | | |
167 | 890 | LabIn.L = LabIn.a = LabIn.b = 0; |
168 | 890 | cmsDoTransform(ContextID, hRoundTrip, &LabIn, &LabOut, 1); |
169 | | |
170 | | // Clip Lab to reasonable limits |
171 | 890 | if (LabOut.L > 50) LabOut.L = 50; |
172 | 890 | LabOut.a = LabOut.b = 0; |
173 | | |
174 | 890 | cmsDeleteTransform(ContextID, hRoundTrip); |
175 | | |
176 | | // Convert it to XYZ |
177 | 890 | cmsLab2XYZ(ContextID, NULL, &BlackXYZ, &LabOut); |
178 | | |
179 | 890 | if (BlackPoint != NULL) |
180 | 890 | *BlackPoint = BlackXYZ; |
181 | | |
182 | 890 | return TRUE; |
183 | 890 | } |
184 | | |
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(cmsContext ContextID, cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags) |
192 | 16.8k | { |
193 | 16.8k | cmsProfileClassSignature devClass; |
194 | | |
195 | | // Make sure the device class is adequate |
196 | 16.8k | devClass = cmsGetDeviceClass(ContextID, hProfile); |
197 | 16.8k | if (devClass == cmsSigLinkClass || |
198 | 16.8k | devClass == cmsSigAbstractClass || |
199 | 16.8k | devClass == cmsSigNamedColorClass) { |
200 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
201 | 0 | return FALSE; |
202 | 0 | } |
203 | | |
204 | | // Make sure intent is adequate |
205 | 16.8k | if (Intent != INTENT_PERCEPTUAL && |
206 | 16.8k | Intent != INTENT_RELATIVE_COLORIMETRIC && |
207 | 16.8k | Intent != INTENT_SATURATION) { |
208 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
209 | 0 | return FALSE; |
210 | 0 | } |
211 | | |
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 | 16.8k | if ((cmsGetEncodedICCversion(ContextID, hProfile) >= 0x4000000) && |
215 | 16.8k | (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) { |
216 | | |
217 | | // Matrix shaper share MRC & perceptual intents |
218 | 0 | if (cmsIsMatrixShaper(ContextID, hProfile)) |
219 | 0 | return BlackPointAsDarkerColorant(ContextID, hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0); |
220 | | |
221 | | // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents |
222 | 0 | BlackPoint -> X = cmsPERCEPTUAL_BLACK_X; |
223 | 0 | BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y; |
224 | 0 | BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z; |
225 | |
|
226 | 0 | return TRUE; |
227 | 0 | } |
228 | | |
229 | | |
230 | | #ifdef CMS_USE_PROFILE_BLACK_POINT_TAG |
231 | | |
232 | | // v2, v4 rel/abs colorimetric |
233 | | if (cmsIsTag(ContextID, hProfile, cmsSigMediaBlackPointTag) && |
234 | | Intent == INTENT_RELATIVE_COLORIMETRIC) { |
235 | | |
236 | | cmsCIEXYZ *BlackPtr, BlackXYZ, UntrustedBlackPoint, TrustedBlackPoint, MediaWhite; |
237 | | cmsCIELab Lab; |
238 | | |
239 | | // If black point is specified, then use it, |
240 | | |
241 | | BlackPtr = cmsReadTag(ContextID, hProfile, cmsSigMediaBlackPointTag); |
242 | | if (BlackPtr != NULL) { |
243 | | |
244 | | BlackXYZ = *BlackPtr; |
245 | | _cmsReadMediaWhitePoint(ContextID, &MediaWhite, hProfile); |
246 | | |
247 | | // Black point is absolute XYZ, so adapt to D50 to get PCS value |
248 | | cmsAdaptToIlluminant(ContextID, &UntrustedBlackPoint, &MediaWhite, cmsD50_XYZ(ContextID), &BlackXYZ); |
249 | | |
250 | | // Force a=b=0 to get rid of any chroma |
251 | | cmsXYZ2Lab(ContextID, NULL, &Lab, &UntrustedBlackPoint); |
252 | | Lab.a = Lab.b = 0; |
253 | | if (Lab.L > 50) Lab.L = 50; // Clip to L* <= 50 |
254 | | cmsLab2XYZ(ContextID, NULL, &TrustedBlackPoint, &Lab); |
255 | | |
256 | | if (BlackPoint != NULL) |
257 | | *BlackPoint = TrustedBlackPoint; |
258 | | |
259 | | return TRUE; |
260 | | } |
261 | | } |
262 | | #endif |
263 | | |
264 | | // That is about v2 profiles. |
265 | | |
266 | | // If output profile, discount ink-limiting and that's all |
267 | 16.8k | if (Intent == INTENT_RELATIVE_COLORIMETRIC && |
268 | 16.8k | (cmsGetDeviceClass(ContextID, hProfile) == cmsSigOutputClass) && |
269 | 16.8k | (cmsGetColorSpace(ContextID, hProfile) == cmsSigCmykData)) |
270 | 890 | return BlackPointUsingPerceptualBlack(ContextID, BlackPoint, hProfile); |
271 | | |
272 | | // Nope, compute BP using current intent. |
273 | 15.9k | return BlackPointAsDarkerColorant(ContextID, hProfile, Intent, BlackPoint, dwFlags); |
274 | 16.8k | } |
275 | | |
276 | | |
277 | | |
278 | | // --------------------------------------------------------------------------------------------------------- |
279 | | |
280 | | // Least Squares Fit of a Quadratic Curve to Data |
281 | | // http://www.personal.psu.edu/jhm/f90/lectures/lsq2.html |
282 | | |
283 | | static |
284 | | cmsFloat64Number RootOfLeastSquaresFitQuadraticCurve(cmsContext ContextID, int n, cmsFloat64Number x[], cmsFloat64Number y[]) |
285 | 17 | { |
286 | 17 | double sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0; |
287 | 17 | double sum_y = 0, sum_yx = 0, sum_yx2 = 0; |
288 | 17 | double d, a, b, c; |
289 | 17 | int i; |
290 | 17 | cmsMAT3 m; |
291 | 17 | cmsVEC3 v, res; |
292 | | |
293 | 17 | if (n < 4) return 0; |
294 | | |
295 | 816 | for (i=0; i < n; i++) { |
296 | | |
297 | 799 | double xn = x[i]; |
298 | 799 | double yn = y[i]; |
299 | | |
300 | 799 | sum_x += xn; |
301 | 799 | sum_x2 += xn*xn; |
302 | 799 | sum_x3 += xn*xn*xn; |
303 | 799 | sum_x4 += xn*xn*xn*xn; |
304 | | |
305 | 799 | sum_y += yn; |
306 | 799 | sum_yx += yn*xn; |
307 | 799 | sum_yx2 += yn*xn*xn; |
308 | 799 | } |
309 | | |
310 | 17 | _cmsVEC3init(ContextID, &m.v[0], n, sum_x, sum_x2); |
311 | 17 | _cmsVEC3init(ContextID, &m.v[1], sum_x, sum_x2, sum_x3); |
312 | 17 | _cmsVEC3init(ContextID, &m.v[2], sum_x2, sum_x3, sum_x4); |
313 | | |
314 | 17 | _cmsVEC3init(ContextID, &v, sum_y, sum_yx, sum_yx2); |
315 | | |
316 | 17 | if (!_cmsMAT3solve(ContextID, &res, &m, &v)) return 0; |
317 | | |
318 | | |
319 | 17 | a = res.n[2]; |
320 | 17 | b = res.n[1]; |
321 | 17 | c = res.n[0]; |
322 | | |
323 | 17 | if (fabs(a) < 1.0E-10) { |
324 | |
|
325 | 0 | if (fabs(b) < 1.0E-10) return 0; |
326 | 0 | return cmsmin(0, cmsmax(50, -c/b )); |
327 | 0 | } |
328 | 17 | else { |
329 | | |
330 | 17 | d = b*b - 4.0 * a * c; |
331 | 17 | if (d <= 0) { |
332 | 0 | return 0; |
333 | 0 | } |
334 | 17 | else { |
335 | | |
336 | 17 | double rt; |
337 | | |
338 | 17 | if (fabs(a) < 1.0E-10) return 0; |
339 | | |
340 | 17 | rt = (-b + sqrt(d)) / (2.0 * a); |
341 | | |
342 | 17 | return cmsmax(0, cmsmin(50, rt)); |
343 | 17 | } |
344 | 17 | } |
345 | | |
346 | 17 | } |
347 | | |
348 | | |
349 | | |
350 | | // Calculates the black point of a destination profile. |
351 | | // This algorithm comes from the Adobe paper disclosing its black point compensation method. |
352 | | cmsBool CMSEXPORT cmsDetectDestinationBlackPoint(cmsContext ContextID, cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags) |
353 | 8.41k | { |
354 | 8.41k | cmsColorSpaceSignature ColorSpace; |
355 | 8.41k | cmsHTRANSFORM hRoundTrip = NULL; |
356 | 8.41k | cmsCIELab InitialLab, destLab, Lab; |
357 | 8.41k | cmsFloat64Number inRamp[256], outRamp[256]; |
358 | 8.41k | cmsFloat64Number MinL, MaxL; |
359 | 8.41k | cmsBool NearlyStraightMidrange = TRUE; |
360 | 8.41k | cmsFloat64Number yRamp[256]; |
361 | 8.41k | cmsFloat64Number x[256], y[256]; |
362 | 8.41k | cmsFloat64Number lo, hi; |
363 | 8.41k | int n, l; |
364 | 8.41k | cmsProfileClassSignature devClass; |
365 | | |
366 | | // Make sure the device class is adequate |
367 | 8.41k | devClass = cmsGetDeviceClass(ContextID, hProfile); |
368 | 8.41k | if (devClass == cmsSigLinkClass || |
369 | 8.41k | devClass == cmsSigAbstractClass || |
370 | 8.41k | devClass == cmsSigNamedColorClass) { |
371 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
372 | 0 | return FALSE; |
373 | 0 | } |
374 | | |
375 | | // Make sure intent is adequate |
376 | 8.41k | if (Intent != INTENT_PERCEPTUAL && |
377 | 8.41k | Intent != INTENT_RELATIVE_COLORIMETRIC && |
378 | 8.41k | Intent != INTENT_SATURATION) { |
379 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
380 | 0 | return FALSE; |
381 | 0 | } |
382 | | |
383 | | |
384 | | // v4 + perceptual & saturation intents does have its own black point, and it is |
385 | | // well specified enough to use it. Black point tag is deprecated in V4. |
386 | 8.41k | if ((cmsGetEncodedICCversion(ContextID, hProfile) >= 0x4000000) && |
387 | 8.41k | (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) { |
388 | | |
389 | | // Matrix shaper share MRC & perceptual intents |
390 | 0 | if (cmsIsMatrixShaper(ContextID, hProfile)) |
391 | 0 | return BlackPointAsDarkerColorant(ContextID, hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0); |
392 | | |
393 | | // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents |
394 | 0 | BlackPoint -> X = cmsPERCEPTUAL_BLACK_X; |
395 | 0 | BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y; |
396 | 0 | BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z; |
397 | 0 | return TRUE; |
398 | 0 | } |
399 | | |
400 | | |
401 | | // Check if the profile is lut based and gray, rgb or cmyk (7.2 in Adobe's document) |
402 | 8.41k | ColorSpace = cmsGetColorSpace(ContextID, hProfile); |
403 | 8.41k | if (!cmsIsCLUT(ContextID, hProfile, Intent, LCMS_USED_AS_OUTPUT ) || |
404 | 8.41k | (ColorSpace != cmsSigGrayData && |
405 | 37 | ColorSpace != cmsSigRgbData && |
406 | 8.38k | ColorSpace != cmsSigCmykData)) { |
407 | | |
408 | | // In this case, handle as input case |
409 | 8.38k | return cmsDetectBlackPoint(ContextID, BlackPoint, hProfile, Intent, dwFlags); |
410 | 8.38k | } |
411 | | |
412 | | // It is one of the valid cases!, use Adobe algorithm |
413 | | |
414 | | |
415 | | // Set a first guess, that should work on good profiles. |
416 | 37 | if (Intent == INTENT_RELATIVE_COLORIMETRIC) { |
417 | | |
418 | 20 | cmsCIEXYZ IniXYZ; |
419 | | |
420 | | // calculate initial Lab as source black point |
421 | 20 | if (!cmsDetectBlackPoint(ContextID, &IniXYZ, hProfile, Intent, dwFlags)) { |
422 | 0 | return FALSE; |
423 | 0 | } |
424 | | |
425 | | // convert the XYZ to lab |
426 | 20 | cmsXYZ2Lab(ContextID, NULL, &InitialLab, &IniXYZ); |
427 | | |
428 | 20 | } else { |
429 | | |
430 | | // set the initial Lab to zero, that should be the black point for perceptual and saturation |
431 | 17 | InitialLab.L = 0; |
432 | 17 | InitialLab.a = 0; |
433 | 17 | InitialLab.b = 0; |
434 | 17 | } |
435 | | |
436 | | |
437 | | // Step 2 |
438 | | // ====== |
439 | | |
440 | | // Create a roundtrip. Define a Transform BT for all x in L*a*b* |
441 | 37 | hRoundTrip = CreateRoundtripXForm(ContextID, hProfile, Intent); |
442 | 37 | if (hRoundTrip == NULL) return FALSE; |
443 | | |
444 | | // Compute ramps |
445 | | |
446 | 9.50k | for (l=0; l < 256; l++) { |
447 | | |
448 | 9.47k | Lab.L = (cmsFloat64Number) (l * 100.0) / 255.0; |
449 | 9.47k | Lab.a = cmsmin(50, cmsmax(-50, InitialLab.a)); |
450 | 9.47k | Lab.b = cmsmin(50, cmsmax(-50, InitialLab.b)); |
451 | | |
452 | 9.47k | cmsDoTransform(ContextID, hRoundTrip, &Lab, &destLab, 1); |
453 | | |
454 | 9.47k | inRamp[l] = Lab.L; |
455 | 9.47k | outRamp[l] = destLab.L; |
456 | 9.47k | } |
457 | | |
458 | | // Make monotonic |
459 | 9.43k | for (l = 254; l > 0; --l) { |
460 | 9.39k | outRamp[l] = cmsmin(outRamp[l], outRamp[l+1]); |
461 | 9.39k | } |
462 | | |
463 | | // Check |
464 | 37 | if (! (outRamp[0] < outRamp[255])) { |
465 | |
|
466 | 0 | cmsDeleteTransform(ContextID, hRoundTrip); |
467 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
468 | 0 | return FALSE; |
469 | 0 | } |
470 | | |
471 | | |
472 | | // Test for mid range straight (only on relative colorimetric) |
473 | 37 | NearlyStraightMidrange = TRUE; |
474 | 37 | MinL = outRamp[0]; MaxL = outRamp[255]; |
475 | 37 | if (Intent == INTENT_RELATIVE_COLORIMETRIC) { |
476 | | |
477 | 5.14k | for (l=0; l < 256; l++) { |
478 | | |
479 | 5.12k | if (! ((inRamp[l] <= MinL + 0.2 * (MaxL - MinL) ) || |
480 | 5.12k | (fabs(inRamp[l] - outRamp[l]) < 4.0 ))) |
481 | 0 | NearlyStraightMidrange = FALSE; |
482 | 5.12k | } |
483 | | |
484 | | // If the mid range is straight (as determined above) then the |
485 | | // DestinationBlackPoint shall be the same as initialLab. |
486 | | // Otherwise, the DestinationBlackPoint shall be determined |
487 | | // using curve fitting. |
488 | 20 | if (NearlyStraightMidrange) { |
489 | | |
490 | 20 | cmsLab2XYZ(ContextID, NULL, BlackPoint, &InitialLab); |
491 | 20 | cmsDeleteTransform(ContextID, hRoundTrip); |
492 | 20 | return TRUE; |
493 | 20 | } |
494 | 20 | } |
495 | | |
496 | | |
497 | | // curve fitting: The round-trip curve normally looks like a nearly constant section at the black point, |
498 | | // with a corner and a nearly straight line to the white point. |
499 | 4.36k | for (l=0; l < 256; l++) { |
500 | | |
501 | 4.35k | yRamp[l] = (outRamp[l] - MinL) / (MaxL - MinL); |
502 | 4.35k | } |
503 | | |
504 | | // find the black point using the least squares error quadratic curve fitting |
505 | 17 | if (Intent == INTENT_RELATIVE_COLORIMETRIC) { |
506 | 0 | lo = 0.1; |
507 | 0 | hi = 0.5; |
508 | 0 | } |
509 | 17 | else { |
510 | | |
511 | | // Perceptual and saturation |
512 | 17 | lo = 0.03; |
513 | 17 | hi = 0.25; |
514 | 17 | } |
515 | | |
516 | | // Capture shadow points for the fitting. |
517 | 17 | n = 0; |
518 | 4.36k | for (l=0; l < 256; l++) { |
519 | | |
520 | 4.35k | cmsFloat64Number ff = yRamp[l]; |
521 | | |
522 | 4.35k | if (ff >= lo && ff < hi) { |
523 | 799 | x[n] = inRamp[l]; |
524 | 799 | y[n] = yRamp[l]; |
525 | 799 | n++; |
526 | 799 | } |
527 | 4.35k | } |
528 | | |
529 | | |
530 | | // No suitable points |
531 | 17 | if (n < 3 ) { |
532 | 0 | cmsDeleteTransform(ContextID, hRoundTrip); |
533 | 0 | BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0; |
534 | 0 | return FALSE; |
535 | 0 | } |
536 | | |
537 | | |
538 | | // fit and get the vertex of quadratic curve |
539 | 17 | Lab.L = RootOfLeastSquaresFitQuadraticCurve(ContextID, n, x, y); |
540 | | |
541 | 17 | if (Lab.L < 0.0) { // clip to zero L* if the vertex is negative |
542 | 0 | Lab.L = 0; |
543 | 0 | } |
544 | | |
545 | 17 | Lab.a = InitialLab.a; |
546 | 17 | Lab.b = InitialLab.b; |
547 | | |
548 | 17 | cmsLab2XYZ(ContextID, NULL, BlackPoint, &Lab); |
549 | | |
550 | 17 | cmsDeleteTransform(ContextID, hRoundTrip); |
551 | 17 | return TRUE; |
552 | 17 | } |