1 //---------------------------------------------------------------------------------
3 // Little Color Management System
4 // Copyright (c) 1998-2012 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 //---------------------------------------------------------------------------------
26 #include "lcms2_internal.h"
28 // Tone curves are powerful constructs that can contain curves specified in diverse ways.
29 // The curve is stored in segments, where each segment can be sampled or specified by parameters.
30 // a 16.bit simplification of the *whole* curve is kept for optimization purposes. For float operation,
31 // each segment is evaluated separately. Plug-ins may be used to define new parametric schemes,
32 // each plug-in may define up to MAX_TYPES_IN_LCMS_PLUGIN functions types. For defining a function,
33 // the plug-in should provide the type id, how many parameters each type has, and a pointer to
34 // a procedure that evaluates the function. In the case of reverse evaluation, the evaluator will
35 // be called with the type id as a negative value, and a sampled version of the reversed curve
38 // ----------------------------------------------------------------- Implementation
39 // Maxim number of nodes
40 #define MAX_NODES_IN_CURVE 4097
41 #define MINUS_INF (-1E22F)
42 #define PLUS_INF (+1E22F)
44 // The list of supported parametric curves
45 typedef struct _cmsParametricCurvesCollection_st {
47 int nFunctions; // Number of supported functions in this chunk
48 int FunctionTypes[MAX_TYPES_IN_LCMS_PLUGIN]; // The identification types
49 int ParameterCount[MAX_TYPES_IN_LCMS_PLUGIN]; // Number of parameters for each function
50 cmsParametricCurveEvaluator Evaluator; // The evaluator
52 struct _cmsParametricCurvesCollection_st* Next; // Next in list
54 } _cmsParametricCurvesCollection;
57 // This is the default (built-in) evaluator
58 static cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Number Params[], cmsFloat64Number R);
61 static _cmsParametricCurvesCollection DefaultCurves = {
62 9, // # of curve types
63 { 1, 2, 3, 4, 5, 6, 7, 8, 108 }, // Parametric curve ID
64 { 1, 3, 4, 5, 7, 4, 5, 5, 1 }, // Parameters by type
65 DefaultEvalParametricFn, // Evaluator
69 // The linked list head
70 static _cmsParametricCurvesCollection* ParametricCurves = &DefaultCurves;
72 // As a way to install new parametric curves
73 cmsBool _cmsRegisterParametricCurvesPlugin(cmsPluginBase* Data)
75 cmsPluginParametricCurves* Plugin = (cmsPluginParametricCurves*) Data;
76 _cmsParametricCurvesCollection* fl;
80 ParametricCurves = &DefaultCurves;
84 fl = (_cmsParametricCurvesCollection*) _cmsPluginMalloc(sizeof(_cmsParametricCurvesCollection));
85 if (fl == NULL) return FALSE;
87 // Copy the parameters
88 fl ->Evaluator = Plugin ->Evaluator;
89 fl ->nFunctions = Plugin ->nFunctions;
91 // Make sure no mem overwrites
92 if (fl ->nFunctions > MAX_TYPES_IN_LCMS_PLUGIN)
93 fl ->nFunctions = MAX_TYPES_IN_LCMS_PLUGIN;
96 memmove(fl->FunctionTypes, Plugin ->FunctionTypes, fl->nFunctions * sizeof(cmsUInt32Number));
97 memmove(fl->ParameterCount, Plugin ->ParameterCount, fl->nFunctions * sizeof(cmsUInt32Number));
100 fl ->Next = ParametricCurves;
101 ParametricCurves = fl;
108 // Search in type list, return position or -1 if not found
110 int IsInSet(int Type, _cmsParametricCurvesCollection* c)
114 for (i=0; i < c ->nFunctions; i++)
115 if (abs(Type) == c ->FunctionTypes[i]) return i;
121 // Search for the collection which contains a specific type
123 _cmsParametricCurvesCollection *GetParametricCurveByType(int Type, int* index)
125 _cmsParametricCurvesCollection* c;
128 for (c = ParametricCurves; c != NULL; c = c ->Next) {
130 Position = IsInSet(Type, c);
132 if (Position != -1) {
142 // Low level allocate, which takes care of memory details. nEntries may be zero, and in this case
143 // no optimation curve is computed. nSegments may also be zero in the inverse case, where only the
144 // optimization curve is given. Both features simultaneously is an error
146 cmsToneCurve* AllocateToneCurveStruct(cmsContext ContextID, cmsInt32Number nEntries,
147 cmsInt32Number nSegments, const cmsCurveSegment* Segments,
148 const cmsUInt16Number* Values)
153 // We allow huge tables, which are then restricted for smoothing operations
154 if (nEntries > 65530 || nEntries < 0) {
155 cmsSignalError(ContextID, cmsERROR_RANGE, "Couldn't create tone curve of more than 65530 entries");
159 if (nEntries <= 0 && nSegments <= 0) {
160 cmsSignalError(ContextID, cmsERROR_RANGE, "Couldn't create tone curve with zero segments and no table");
164 // Allocate all required pointers, etc.
165 p = (cmsToneCurve*) _cmsMallocZero(ContextID, sizeof(cmsToneCurve));
168 // In this case, there are no segments
169 if (nSegments <= 0) {
174 p ->Segments = (cmsCurveSegment*) _cmsCalloc(ContextID, nSegments, sizeof(cmsCurveSegment));
175 if (p ->Segments == NULL) goto Error;
177 p ->Evals = (cmsParametricCurveEvaluator*) _cmsCalloc(ContextID, nSegments, sizeof(cmsParametricCurveEvaluator));
178 if (p ->Evals == NULL) goto Error;
181 p -> nSegments = nSegments;
183 // This 16-bit table contains a limited precision representation of the whole curve and is kept for
184 // increasing xput on certain operations.
189 p ->Table16 = (cmsUInt16Number*) _cmsCalloc(ContextID, nEntries, sizeof(cmsUInt16Number));
190 if (p ->Table16 == NULL) goto Error;
193 p -> nEntries = nEntries;
195 // Initialize members if requested
196 if (Values != NULL && (nEntries > 0)) {
198 for (i=0; i < nEntries; i++)
199 p ->Table16[i] = Values[i];
202 // Initialize the segments stuff. The evaluator for each segment is located and a pointer to it
203 // is placed in advance to maximize performance.
204 if (Segments != NULL && (nSegments > 0)) {
206 _cmsParametricCurvesCollection *c;
208 p ->SegInterp = (cmsInterpParams**) _cmsCalloc(ContextID, nSegments, sizeof(cmsInterpParams*));
209 if (p ->SegInterp == NULL) goto Error;
211 for (i=0; i< nSegments; i++) {
213 // Type 0 is a special marker for table-based curves
214 if (Segments[i].Type == 0)
215 p ->SegInterp[i] = _cmsComputeInterpParams(ContextID, Segments[i].nGridPoints, 1, 1, NULL, CMS_LERP_FLAGS_FLOAT);
217 memmove(&p ->Segments[i], &Segments[i], sizeof(cmsCurveSegment));
219 if (Segments[i].Type == 0 && Segments[i].SampledPoints != NULL)
220 p ->Segments[i].SampledPoints = (cmsFloat32Number*) _cmsDupMem(ContextID, Segments[i].SampledPoints, sizeof(cmsFloat32Number) * Segments[i].nGridPoints);
222 p ->Segments[i].SampledPoints = NULL;
225 c = GetParametricCurveByType(Segments[i].Type, NULL);
227 p ->Evals[i] = c ->Evaluator;
231 p ->InterpParams = _cmsComputeInterpParams(ContextID, p ->nEntries, 1, 1, p->Table16, CMS_LERP_FLAGS_16BITS);
235 if (p -> Segments) _cmsFree(ContextID, p ->Segments);
236 if (p -> Evals) _cmsFree(ContextID, p -> Evals);
237 if (p ->Table16) _cmsFree(ContextID, p ->Table16);
238 _cmsFree(ContextID, p);
243 // Parametric Fn using floating point
245 cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Number Params[], cmsFloat64Number R)
247 cmsFloat64Number e, Val, disc;
255 if (fabs(Params[0] - 1.0) < MATRIX_DET_TOLERANCE)
261 Val = pow(R, Params[0]);
264 // Type 1 Reversed: X = Y ^1/gamma
268 if (fabs(Params[0] - 1.0) < MATRIX_DET_TOLERANCE)
274 Val = pow(R, 1/Params[0]);
278 // Y = (aX + b)^Gamma | X >= -b/a
281 disc = -Params[2] / Params[1];
285 e = Params[1]*R + Params[2];
288 Val = pow(e, Params[0]);
297 // X = (Y ^1/g - b) / a
302 Val = (pow(R, 1.0/Params[0]) - Params[2]) / Params[1];
310 // Y = (aX + b)^Gamma | X <= -b/a
313 disc = -Params[2] / Params[1];
319 e = Params[1]*R + Params[2];
322 Val = pow(e, Params[0]) + Params[3];
332 // X=((Y-c)^1/g - b)/a | (Y>=c)
335 if (R >= Params[3]) {
340 Val = (pow(e, 1/Params[0]) - Params[2]) / Params[1];
345 Val = -Params[2] / Params[1];
350 // IEC 61966-2.1 (sRGB)
351 // Y = (aX + b)^Gamma | X >= d
354 if (R >= Params[4]) {
356 e = Params[1]*R + Params[2];
359 Val = pow(e, Params[0]);
368 // X=((Y^1/g-b)/a) | Y >= (ad+b)^g
369 // X=Y/c | Y< (ad+b)^g
371 e = Params[1] * Params[4] + Params[2];
375 disc = pow(e, Params[0]);
379 Val = (pow(R, 1.0/Params[0]) - Params[2]) / Params[1];
387 // Y = (aX + b)^Gamma + e | X >= d
388 // Y = cX + f | X < d
390 if (R >= Params[4]) {
392 e = Params[1]*R + Params[2];
395 Val = pow(e, Params[0]) + Params[5];
400 Val = R*Params[3] + Params[6];
405 // X=((Y-e)1/g-b)/a | Y >=(ad+b)^g+e), cd+f
409 disc = Params[3] * Params[4] + Params[6];
416 Val = (pow(e, 1.0/Params[0]) - Params[2]) / Params[1];
419 Val = (R - Params[6]) / Params[3];
424 // Types 6,7,8 comes from segmented curves as described in ICCSpecRevision_02_11_06_Float.pdf
425 // Type 6 is basically identical to type 5 without d
427 // Y = (a * X + b) ^ Gamma + c
429 e = Params[1]*R + Params[2];
434 Val = pow(e, Params[0]) + Params[3];
437 // ((Y - c) ^1/Gamma - b) / a
443 Val = (pow(e, 1.0/Params[0]) - Params[2]) / Params[1];
447 // Y = a * log (b * X^Gamma + c) + d
450 e = Params[2] * pow(R, Params[0]) + Params[3];
454 Val = Params[1]*log10(e) + Params[4];
457 // (Y - d) / a = log(b * X ^Gamma + c)
458 // pow(10, (Y-d) / a) = b * X ^Gamma + c
459 // pow((pow(10, (Y-d) / a) - c) / b, 1/g) = X
461 Val = pow((pow(10.0, (R-Params[4]) / Params[1]) - Params[3]) / Params[2], 1.0 / Params[0]);
465 //Y = a * b^(c*X+d) + e
467 Val = (Params[0] * pow(Params[1], Params[2] * R + Params[3]) + Params[4]);
471 // Y = (log((y-e) / a) / log(b) - d ) / c
472 // a=0, b=1, c=2, d=3, e=4,
475 disc = R - Params[4];
476 if (disc < 0) Val = 0;
478 Val = (log(disc / Params[0]) / log(Params[1]) - Params[3]) / Params[2];
481 // S-Shaped: (1 - (1-x)^1/g)^1/g
483 Val = pow(1.0 - pow(1 - R, 1/Params[0]), 1/Params[0]);
486 // y = (1 - (1-x)^1/g)^1/g
487 // y^g = (1 - (1-x)^1/g)
488 // 1 - y^g = (1-x)^1/g
489 // (1 - y^g)^g = 1 - x
492 Val = 1 - pow(1 - pow(R, Params[0]), Params[0]);
496 // Unsupported parametric curve. Should never reach here
503 // Evaluate a segmented funtion for a single value. Return -1 if no valid segment found .
504 // If fn type is 0, perform an interpolation on the table
506 cmsFloat64Number EvalSegmentedFn(const cmsToneCurve *g, cmsFloat64Number R)
510 for (i = g ->nSegments-1; i >= 0 ; --i) {
513 if ((R > g ->Segments[i].x0) && (R <= g ->Segments[i].x1)) {
515 // Type == 0 means segment is sampled
516 if (g ->Segments[i].Type == 0) {
518 cmsFloat32Number R1 = (cmsFloat32Number) (R - g ->Segments[i].x0);
519 cmsFloat32Number Out;
521 // Setup the table (TODO: clean that)
522 g ->SegInterp[i]-> Table = g ->Segments[i].SampledPoints;
524 g ->SegInterp[i] -> Interpolation.LerpFloat(&R1, &Out, g ->SegInterp[i]);
529 return g ->Evals[i](g->Segments[i].Type, g ->Segments[i].Params, R);
536 // Access to estimated low-res table
537 cmsUInt32Number CMSEXPORT cmsGetToneCurveEstimatedTableEntries(const cmsToneCurve* t)
539 _cmsAssert(t != NULL);
543 const cmsUInt16Number* CMSEXPORT cmsGetToneCurveEstimatedTable(const cmsToneCurve* t)
545 _cmsAssert(t != NULL);
550 // Create an empty gamma curve, by using tables. This specifies only the limited-precision part, and leaves the
551 // floating point description empty.
552 cmsToneCurve* CMSEXPORT cmsBuildTabulatedToneCurve16(cmsContext ContextID, cmsInt32Number nEntries, const cmsUInt16Number Values[])
554 return AllocateToneCurveStruct(ContextID, nEntries, 0, NULL, Values);
558 int EntriesByGamma(cmsFloat64Number Gamma)
560 if (fabs(Gamma - 1.0) < 0.001) return 2;
565 // Create a segmented gamma, fill the table
566 cmsToneCurve* CMSEXPORT cmsBuildSegmentedToneCurve(cmsContext ContextID,
567 cmsInt32Number nSegments, const cmsCurveSegment Segments[])
570 cmsFloat64Number R, Val;
572 int nGridPoints = 4096;
574 _cmsAssert(Segments != NULL);
576 // Optimizatin for identity curves.
577 if (nSegments == 1 && Segments[0].Type == 1) {
579 nGridPoints = EntriesByGamma(Segments[0].Params[0]);
582 g = AllocateToneCurveStruct(ContextID, nGridPoints, nSegments, Segments, NULL);
583 if (g == NULL) return NULL;
585 // Once we have the floating point version, we can approximate a 16 bit table of 4096 entries
586 // for performance reasons. This table would normally not be used except on 8/16 bits transforms.
587 for (i=0; i < nGridPoints; i++) {
589 R = (cmsFloat64Number) i / (nGridPoints-1);
591 Val = EvalSegmentedFn(g, R);
593 // Round and saturate
594 g ->Table16[i] = _cmsQuickSaturateWord(Val * 65535.0);
600 // Use a segmented curve to store the floating point table
601 cmsToneCurve* CMSEXPORT cmsBuildTabulatedToneCurveFloat(cmsContext ContextID, cmsUInt32Number nEntries, const cmsFloat32Number values[])
603 cmsCurveSegment Seg[2];
605 // Initialize segmented curve part up to 0
610 Seg[0].Params[0] = 1;
611 Seg[0].Params[1] = 0;
612 Seg[0].Params[2] = 0;
613 Seg[0].Params[3] = 0;
614 Seg[0].Params[4] = 0;
621 Seg[1].nGridPoints = nEntries;
622 Seg[1].SampledPoints = (cmsFloat32Number*) values;
624 return cmsBuildSegmentedToneCurve(ContextID, 2, Seg);
629 // Parameters goes as: Curve, a, b, c, d, e, f
630 // Type is the ICC type +1
631 // if type is negative, then the curve is analyticaly inverted
632 cmsToneCurve* CMSEXPORT cmsBuildParametricToneCurve(cmsContext ContextID, cmsInt32Number Type, const cmsFloat64Number Params[])
634 cmsCurveSegment Seg0;
636 cmsUInt32Number size;
637 _cmsParametricCurvesCollection* c = GetParametricCurveByType(Type, &Pos);
639 _cmsAssert(Params != NULL);
642 cmsSignalError(ContextID, cmsERROR_UNKNOWN_EXTENSION, "Invalid parametric curve type %d", Type);
646 memset(&Seg0, 0, sizeof(Seg0));
652 size = c->ParameterCount[Pos] * sizeof(cmsFloat64Number);
653 memmove(Seg0.Params, Params, size);
655 return cmsBuildSegmentedToneCurve(ContextID, 1, &Seg0);
660 // Build a gamma table based on gamma constant
661 cmsToneCurve* CMSEXPORT cmsBuildGamma(cmsContext ContextID, cmsFloat64Number Gamma)
663 return cmsBuildParametricToneCurve(ContextID, 1, &Gamma);
667 // Free all memory taken by the gamma curve
668 void CMSEXPORT cmsFreeToneCurve(cmsToneCurve* Curve)
670 cmsContext ContextID;
672 if (Curve == NULL) return;
674 ContextID = Curve ->InterpParams->ContextID;
676 _cmsFreeInterpParams(Curve ->InterpParams);
678 if (Curve -> Table16)
679 _cmsFree(ContextID, Curve ->Table16);
681 if (Curve ->Segments) {
685 for (i=0; i < Curve ->nSegments; i++) {
687 if (Curve ->Segments[i].SampledPoints) {
688 _cmsFree(ContextID, Curve ->Segments[i].SampledPoints);
691 if (Curve ->SegInterp[i] != 0)
692 _cmsFreeInterpParams(Curve->SegInterp[i]);
695 _cmsFree(ContextID, Curve ->Segments);
696 _cmsFree(ContextID, Curve ->SegInterp);
700 _cmsFree(ContextID, Curve -> Evals);
702 if (Curve) _cmsFree(ContextID, Curve);
705 // Utility function, free 3 gamma tables
706 void CMSEXPORT cmsFreeToneCurveTriple(cmsToneCurve* Curve[3])
709 _cmsAssert(Curve != NULL);
711 if (Curve[0] != NULL) cmsFreeToneCurve(Curve[0]);
712 if (Curve[1] != NULL) cmsFreeToneCurve(Curve[1]);
713 if (Curve[2] != NULL) cmsFreeToneCurve(Curve[2]);
715 Curve[0] = Curve[1] = Curve[2] = NULL;
719 // Duplicate a gamma table
720 cmsToneCurve* CMSEXPORT cmsDupToneCurve(const cmsToneCurve* In)
722 if (In == NULL) return NULL;
724 return AllocateToneCurveStruct(In ->InterpParams ->ContextID, In ->nEntries, In ->nSegments, In ->Segments, In ->Table16);
727 // Joins two curves for X and Y. Curves should be monotonic.
732 cmsToneCurve* CMSEXPORT cmsJoinToneCurve(cmsContext ContextID,
733 const cmsToneCurve* X,
734 const cmsToneCurve* Y, cmsUInt32Number nResultingPoints)
736 cmsToneCurve* out = NULL;
737 cmsToneCurve* Yreversed = NULL;
738 cmsFloat32Number t, x;
739 cmsFloat32Number* Res = NULL;
743 _cmsAssert(X != NULL);
744 _cmsAssert(Y != NULL);
746 Yreversed = cmsReverseToneCurveEx(nResultingPoints, Y);
747 if (Yreversed == NULL) goto Error;
749 Res = (cmsFloat32Number*) _cmsCalloc(ContextID, nResultingPoints, sizeof(cmsFloat32Number));
750 if (Res == NULL) goto Error;
753 for (i=0; i < nResultingPoints; i++) {
755 t = (cmsFloat32Number) i / (nResultingPoints-1);
756 x = cmsEvalToneCurveFloat(X, t);
757 Res[i] = cmsEvalToneCurveFloat(Yreversed, x);
760 // Allocate space for output
761 out = cmsBuildTabulatedToneCurveFloat(ContextID, nResultingPoints, Res);
765 if (Res != NULL) _cmsFree(ContextID, Res);
766 if (Yreversed != NULL) cmsFreeToneCurve(Yreversed);
773 // Get the surrounding nodes. This is tricky on non-monotonic tables
775 int GetInterval(cmsFloat64Number In, const cmsUInt16Number LutTable[], const struct _cms_interp_struc* p)
780 // A 1 point table is not allowed
781 if (p -> Domain[0] < 1) return -1;
783 // Let's see if ascending or descending.
784 if (LutTable[0] < LutTable[p ->Domain[0]]) {
786 // Table is overall ascending
787 for (i=p->Domain[0]-1; i >=0; --i) {
792 if (y0 <= y1) { // Increasing
793 if (In >= y0 && In <= y1) return i;
796 if (y1 < y0) { // Decreasing
797 if (In >= y1 && In <= y0) return i;
802 // Table is overall descending
803 for (i=0; i < (int) p -> Domain[0]; i++) {
808 if (y0 <= y1) { // Increasing
809 if (In >= y0 && In <= y1) return i;
812 if (y1 < y0) { // Decreasing
813 if (In >= y1 && In <= y0) return i;
821 // Reverse a gamma table
822 cmsToneCurve* CMSEXPORT cmsReverseToneCurveEx(cmsInt32Number nResultSamples, const cmsToneCurve* InCurve)
825 cmsFloat64Number a = 0, b = 0, y, x1, y1, x2, y2;
829 _cmsAssert(InCurve != NULL);
831 // Try to reverse it analytically whatever possible
832 if (InCurve ->nSegments == 1 && InCurve ->Segments[0].Type > 0 && InCurve -> Segments[0].Type <= 5) {
834 return cmsBuildParametricToneCurve(InCurve ->InterpParams->ContextID,
835 -(InCurve -> Segments[0].Type),
836 InCurve -> Segments[0].Params);
839 // Nope, reverse the table.
840 out = cmsBuildTabulatedToneCurve16(InCurve ->InterpParams->ContextID, nResultSamples, NULL);
844 // We want to know if this is an ascending or descending table
845 Ascending = !cmsIsToneCurveDescending(InCurve);
847 // Iterate across Y axis
848 for (i=0; i < nResultSamples; i++) {
850 y = (cmsFloat64Number) i * 65535.0 / (nResultSamples - 1);
852 // Find interval in which y is within.
853 j = GetInterval(y, InCurve->Table16, InCurve->InterpParams);
857 // Get limits of interval
858 x1 = InCurve ->Table16[j];
859 x2 = InCurve ->Table16[j+1];
861 y1 = (cmsFloat64Number) (j * 65535.0) / (InCurve ->nEntries - 1);
862 y2 = (cmsFloat64Number) ((j+1) * 65535.0 ) / (InCurve ->nEntries - 1);
864 // If collapsed, then use any
867 out ->Table16[i] = _cmsQuickSaturateWord(Ascending ? y2 : y1);
873 a = (y2 - y1) / (x2 - x1);
878 out ->Table16[i] = _cmsQuickSaturateWord(a* y + b);
885 // Reverse a gamma table
886 cmsToneCurve* CMSEXPORT cmsReverseToneCurve(const cmsToneCurve* InGamma)
888 _cmsAssert(InGamma != NULL);
890 return cmsReverseToneCurveEx(4096, InGamma);
893 // From: Eilers, P.H.C. (1994) Smoothing and interpolation with finite
894 // differences. in: Graphic Gems IV, Heckbert, P.S. (ed.), Academic press.
896 // Smoothing and interpolation with second differences.
898 // Input: weights (w), data (y): vector from 1 to m.
899 // Input: smoothing parameter (lambda), length (m).
900 // Output: smoothed vector (z): vector from 1 to m.
903 cmsBool smooth2(cmsContext ContextID, cmsFloat32Number w[], cmsFloat32Number y[], cmsFloat32Number z[], cmsFloat32Number lambda, int m)
906 cmsFloat32Number *c, *d, *e;
910 c = (cmsFloat32Number*) _cmsCalloc(ContextID, MAX_NODES_IN_CURVE, sizeof(cmsFloat32Number));
911 d = (cmsFloat32Number*) _cmsCalloc(ContextID, MAX_NODES_IN_CURVE, sizeof(cmsFloat32Number));
912 e = (cmsFloat32Number*) _cmsCalloc(ContextID, MAX_NODES_IN_CURVE, sizeof(cmsFloat32Number));
914 if (c != NULL && d != NULL && e != NULL) {
917 d[1] = w[1] + lambda;
918 c[1] = -2 * lambda / d[1];
921 d[2] = w[2] + 5 * lambda - d[1] * c[1] * c[1];
922 c[2] = (-4 * lambda - d[1] * c[1] * e[1]) / d[2];
923 e[2] = lambda / d[2];
924 z[2] = w[2] * y[2] - c[1] * z[1];
926 for (i = 3; i < m - 1; i++) {
927 i1 = i - 1; i2 = i - 2;
928 d[i]= w[i] + 6 * lambda - c[i1] * c[i1] * d[i1] - e[i2] * e[i2] * d[i2];
929 c[i] = (-4 * lambda -d[i1] * c[i1] * e[i1])/ d[i];
930 e[i] = lambda / d[i];
931 z[i] = w[i] * y[i] - c[i1] * z[i1] - e[i2] * z[i2];
934 i1 = m - 2; i2 = m - 3;
936 d[m - 1] = w[m - 1] + 5 * lambda -c[i1] * c[i1] * d[i1] - e[i2] * e[i2] * d[i2];
937 c[m - 1] = (-2 * lambda - d[i1] * c[i1] * e[i1]) / d[m - 1];
938 z[m - 1] = w[m - 1] * y[m - 1] - c[i1] * z[i1] - e[i2] * z[i2];
939 i1 = m - 1; i2 = m - 2;
941 d[m] = w[m] + lambda - c[i1] * c[i1] * d[i1] - e[i2] * e[i2] * d[i2];
942 z[m] = (w[m] * y[m] - c[i1] * z[i1] - e[i2] * z[i2]) / d[m];
943 z[m - 1] = z[m - 1] / d[m - 1] - c[m - 1] * z[m];
945 for (i = m - 2; 1<= i; i--)
946 z[i] = z[i] / d[i] - c[i] * z[i + 1] - e[i] * z[i + 2];
952 if (c != NULL) _cmsFree(ContextID, c);
953 if (d != NULL) _cmsFree(ContextID, d);
954 if (e != NULL) _cmsFree(ContextID, e);
959 // Smooths a curve sampled at regular intervals.
960 cmsBool CMSEXPORT cmsSmoothToneCurve(cmsToneCurve* Tab, cmsFloat64Number lambda)
962 cmsFloat32Number w[MAX_NODES_IN_CURVE], y[MAX_NODES_IN_CURVE], z[MAX_NODES_IN_CURVE];
963 int i, nItems, Zeros, Poles;
965 if (Tab == NULL) return FALSE;
967 if (cmsIsToneCurveLinear(Tab)) return FALSE; // Nothing to do
969 nItems = Tab -> nEntries;
971 if (nItems >= MAX_NODES_IN_CURVE) {
972 cmsSignalError(Tab ->InterpParams->ContextID, cmsERROR_RANGE, "cmsSmoothToneCurve: too many points.");
976 memset(w, 0, nItems * sizeof(cmsFloat32Number));
977 memset(y, 0, nItems * sizeof(cmsFloat32Number));
978 memset(z, 0, nItems * sizeof(cmsFloat32Number));
980 for (i=0; i < nItems; i++)
982 y[i+1] = (cmsFloat32Number) Tab -> Table16[i];
986 if (!smooth2(Tab ->InterpParams->ContextID, w, y, z, (cmsFloat32Number) lambda, nItems)) return FALSE;
988 // Do some reality - checking...
990 for (i=nItems; i > 1; --i) {
992 if (z[i] == 0.) Zeros++;
993 if (z[i] >= 65535.) Poles++;
994 if (z[i] < z[i-1]) return FALSE; // Non-Monotonic
997 if (Zeros > (nItems / 3)) return FALSE; // Degenerated, mostly zeros
998 if (Poles > (nItems / 3)) return FALSE; // Degenerated, mostly poles
1001 for (i=0; i < nItems; i++) {
1003 // Clamp to cmsUInt16Number
1004 Tab -> Table16[i] = _cmsQuickSaturateWord(z[i+1]);
1010 // Is a table linear? Do not use parametric since we cannot guarantee some weird parameters resulting
1011 // in a linear table. This way assures it is linear in 12 bits, which should be enought in most cases.
1012 cmsBool CMSEXPORT cmsIsToneCurveLinear(const cmsToneCurve* Curve)
1017 _cmsAssert(Curve != NULL);
1019 for (i=0; i < Curve ->nEntries; i++) {
1021 diff = abs((int) Curve->Table16[i] - (int) _cmsQuantizeVal(i, Curve ->nEntries));
1029 // Same, but for monotonicity
1030 cmsBool CMSEXPORT cmsIsToneCurveMonotonic(const cmsToneCurve* t)
1034 cmsBool lDescending;
1036 _cmsAssert(t != NULL);
1038 // Degenerated curves are monotonic? Ok, let's pass them
1040 if (n < 2) return TRUE;
1043 lDescending = cmsIsToneCurveDescending(t);
1047 last = t ->Table16[0];
1049 for (i = 1; i < n; i++) {
1051 if (t ->Table16[i] - last > 2) // We allow some ripple
1054 last = t ->Table16[i];
1060 last = t ->Table16[n-1];
1062 for (i = n-2; i >= 0; --i) {
1064 if (t ->Table16[i] - last > 2)
1067 last = t ->Table16[i];
1075 // Same, but for descending tables
1076 cmsBool CMSEXPORT cmsIsToneCurveDescending(const cmsToneCurve* t)
1078 _cmsAssert(t != NULL);
1080 return t ->Table16[0] > t ->Table16[t ->nEntries-1];
1084 // Another info fn: is out gamma table multisegment?
1085 cmsBool CMSEXPORT cmsIsToneCurveMultisegment(const cmsToneCurve* t)
1087 _cmsAssert(t != NULL);
1089 return t -> nSegments > 1;
1092 cmsInt32Number CMSEXPORT cmsGetToneCurveParametricType(const cmsToneCurve* t)
1094 _cmsAssert(t != NULL);
1096 if (t -> nSegments != 1) return 0;
1097 return t ->Segments[0].Type;
1100 // We need accuracy this time
1101 cmsFloat32Number CMSEXPORT cmsEvalToneCurveFloat(const cmsToneCurve* Curve, cmsFloat32Number v)
1103 _cmsAssert(Curve != NULL);
1105 // Check for 16 bits table. If so, this is a limited-precision tone curve
1106 if (Curve ->nSegments == 0) {
1108 cmsUInt16Number In, Out;
1110 In = (cmsUInt16Number) _cmsQuickSaturateWord(v * 65535.0);
1111 Out = cmsEvalToneCurve16(Curve, In);
1113 return (cmsFloat32Number) (Out / 65535.0);
1116 return (cmsFloat32Number) EvalSegmentedFn(Curve, v);
1119 // We need xput over here
1120 cmsUInt16Number CMSEXPORT cmsEvalToneCurve16(const cmsToneCurve* Curve, cmsUInt16Number v)
1122 cmsUInt16Number out;
1124 _cmsAssert(Curve != NULL);
1126 Curve ->InterpParams ->Interpolation.Lerp16(&v, &out, Curve ->InterpParams);
1131 // Least squares fitting.
1132 // A mathematical procedure for finding the best-fitting curve to a given set of points by
1133 // minimizing the sum of the squares of the offsets ("the residuals") of the points from the curve.
1134 // The sum of the squares of the offsets is used instead of the offset absolute values because
1135 // this allows the residuals to be treated as a continuous differentiable quantity.
1139 // R = (yi - (xi^g))
1140 // R2 = (yi - (xi^g))2
1141 // SUM R2 = SUM (yi - (xi^g))2
1143 // dR2/dg = -2 SUM x^g log(x)(y - x^g)
1144 // solving for dR2/dg = 0
1146 // g = 1/n * SUM(log(y) / log(x))
1148 cmsFloat64Number CMSEXPORT cmsEstimateGamma(const cmsToneCurve* t, cmsFloat64Number Precision)
1150 cmsFloat64Number gamma, sum, sum2;
1151 cmsFloat64Number n, x, y, Std;
1154 _cmsAssert(t != NULL);
1158 // Excluding endpoints
1159 for (i=1; i < (MAX_NODES_IN_CURVE-1); i++) {
1161 x = (cmsFloat64Number) i / (MAX_NODES_IN_CURVE-1);
1162 y = (cmsFloat64Number) cmsEvalToneCurveFloat(t, (cmsFloat32Number) x);
1164 // Avoid 7% on lower part to prevent
1165 // artifacts due to linear ramps
1167 if (y > 0. && y < 1. && x > 0.07) {
1169 gamma = log(y) / log(x);
1171 sum2 += gamma * gamma;
1176 // Take a look on SD to see if gamma isn't exponential at all
1177 Std = sqrt((n * sum2 - sum * sum) / (n*(n-1)));
1179 if (Std > Precision)
1182 return (sum / n); // The mean