diff options
Diffstat (limited to 'src/cmsgamma.c')
-rw-r--r-- | src/cmsgamma.c | 224 |
1 files changed, 112 insertions, 112 deletions
diff --git a/src/cmsgamma.c b/src/cmsgamma.c index b546fd8..da902f7 100644 --- a/src/cmsgamma.c +++ b/src/cmsgamma.c @@ -3,40 +3,40 @@ // 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 +// 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 +// 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 +// 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" -// Tone curves are powerful constructs that can contain curves specified in diverse ways. +// Tone curves are powerful constructs that can contain curves specified in diverse ways. // The curve is stored in segments, where each segment can be sampled or specified by parameters. -// a 16.bit simplification of the *whole* curve is kept for optimization purposes. For float operation, -// each segment is evaluated separately. Plug-ins may be used to define new parametric schemes, -// each plug-in may define up to MAX_TYPES_IN_LCMS_PLUGIN functions types. For defining a function, +// a 16.bit simplification of the *whole* curve is kept for optimization purposes. For float operation, +// each segment is evaluated separately. Plug-ins may be used to define new parametric schemes, +// each plug-in may define up to MAX_TYPES_IN_LCMS_PLUGIN functions types. For defining a function, // the plug-in should provide the type id, how many parameters each type has, and a pointer to -// a procedure that evaluates the function. In the case of reverse evaluation, the evaluator will -// be called with the type id as a negative value, and a sampled version of the reversed curve +// a procedure that evaluates the function. In the case of reverse evaluation, the evaluator will +// be called with the type id as a negative value, and a sampled version of the reversed curve // will be built. // ----------------------------------------------------------------- Implementation -// Maxim number of nodes +// Maxim number of nodes #define MAX_NODES_IN_CURVE 4097 #define MINUS_INF (-1E22F) #define PLUS_INF (+1E22F) @@ -54,11 +54,11 @@ typedef struct _cmsParametricCurvesCollection_st { } _cmsParametricCurvesCollection; -// This is the default (built-in) evaluator +// This is the default (built-in) evaluator static cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Number Params[], cmsFloat64Number R); // The built-in list -static _cmsParametricCurvesCollection DefaultCurves = { +static _cmsParametricCurvesCollection DefaultCurves = { 9, // # of curve types { 1, 2, 3, 4, 5, 6, 7, 8, 108 }, // Parametric curve ID { 1, 3, 4, 5, 7, 4, 5, 5, 1 }, // Parameters by type @@ -74,9 +74,9 @@ cmsBool _cmsRegisterParametricCurvesPlugin(cmsPluginBase* Data) { cmsPluginParametricCurves* Plugin = (cmsPluginParametricCurves*) Data; _cmsParametricCurvesCollection* fl; - + if (Data == NULL) { - + ParametricCurves = &DefaultCurves; return TRUE; } @@ -130,7 +130,7 @@ _cmsParametricCurvesCollection *GetParametricCurveByType(int Type, int* index) Position = IsInSet(Type, c); if (Position != -1) { - if (index != NULL) + if (index != NULL) *index = Position; return c; } @@ -139,12 +139,12 @@ _cmsParametricCurvesCollection *GetParametricCurveByType(int Type, int* index) return NULL; } -// Low level allocate, which takes care of memory details. nEntries may be zero, and in this case +// Low level allocate, which takes care of memory details. nEntries may be zero, and in this case // no optimation curve is computed. nSegments may also be zero in the inverse case, where only the // optimization curve is given. Both features simultaneously is an error static -cmsToneCurve* AllocateToneCurveStruct(cmsContext ContextID, cmsInt32Number nEntries, - cmsInt32Number nSegments, const cmsCurveSegment* Segments, +cmsToneCurve* AllocateToneCurveStruct(cmsContext ContextID, cmsInt32Number nEntries, + cmsInt32Number nSegments, const cmsCurveSegment* Segments, const cmsUInt16Number* Values) { cmsToneCurve* p; @@ -179,7 +179,7 @@ cmsToneCurve* AllocateToneCurveStruct(cmsContext ContextID, cmsInt32Number nEntr } p -> nSegments = nSegments; - + // This 16-bit table contains a limited precision representation of the whole curve and is kept for // increasing xput on certain operations. if (nEntries <= 0) { @@ -189,13 +189,13 @@ cmsToneCurve* AllocateToneCurveStruct(cmsContext ContextID, cmsInt32Number nEntr p ->Table16 = (cmsUInt16Number*) _cmsCalloc(ContextID, nEntries, sizeof(cmsUInt16Number)); if (p ->Table16 == NULL) goto Error; } - + p -> nEntries = nEntries; - + // Initialize members if requested if (Values != NULL && (nEntries > 0)) { - for (i=0; i < nEntries; i++) + for (i=0; i < nEntries; i++) p ->Table16[i] = Values[i]; } @@ -227,7 +227,7 @@ cmsToneCurve* AllocateToneCurveStruct(cmsContext ContextID, cmsInt32Number nEntr p ->Evals[i] = c ->Evaluator; } } - + p ->InterpParams = _cmsComputeInterpParams(ContextID, p ->nEntries, 1, 1, p->Table16, CMS_LERP_FLAGS_16BITS); return p; @@ -249,7 +249,7 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu switch (Type) { // X = Y ^ Gamma - case 1: + case 1: if (R < 0) { if (fabs(Params[0] - 1.0) < MATRIX_DET_TOLERANCE) @@ -295,14 +295,14 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu // Type 2 Reversed // X = (Y ^1/g - b) / a - case -2: + case -2: if (R < 0) Val = 0; else Val = (pow(R, 1.0/Params[0]) - Params[2]) / Params[1]; if (Val < 0) - Val = 0; + Val = 0; break; @@ -316,7 +316,7 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu if (R >= disc) { - e = Params[1]*R + Params[2]; + e = Params[1]*R + Params[2]; if (e > 0) Val = pow(e, Params[0]) + Params[3]; @@ -330,15 +330,15 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu // Type 3 reversed // X=((Y-c)^1/g - b)/a | (Y>=c) - // X=-b/a | (Y<c) + // X=-b/a | (Y<c) case -3: if (R >= Params[3]) { - + e = R - Params[3]; if (e > 0) Val = (pow(e, 1/Params[0]) - Params[2]) / Params[1]; - else + else Val = 0; } else { @@ -395,7 +395,7 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu Val = pow(e, Params[0]) + Params[5]; else Val = 0; - } + } else Val = R*Params[3] + Params[6]; break; @@ -410,7 +410,7 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu if (R >= disc) { e = R - Params[5]; - if (e < 0) + if (e < 0) Val = 0; else Val = (pow(e, 1.0/Params[0]) - Params[2]) / Params[1]; @@ -423,29 +423,29 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu // Types 6,7,8 comes from segmented curves as described in ICCSpecRevision_02_11_06_Float.pdf // Type 6 is basically identical to type 5 without d - + // Y = (a * X + b) ^ Gamma + c - case 6: + case 6: e = Params[1]*R + Params[2]; - if (e < 0) + if (e < 0) Val = 0; - else + else Val = pow(e, Params[0]) + Params[3]; break; - // ((Y - c) ^1/Gamma - b) / a + // ((Y - c) ^1/Gamma - b) / a case -6: e = R - Params[3]; if (e < 0) Val = 0; - else + else Val = (pow(e, 1.0/Params[0]) - Params[2]) / Params[1]; break; // Y = a * log (b * X^Gamma + c) + d - case 7: + case 7: e = Params[2] * pow(R, Params[0]) + Params[3]; if (e <= 0) @@ -456,13 +456,13 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu // (Y - d) / a = log(b * X ^Gamma + c) // pow(10, (Y-d) / a) = b * X ^Gamma + c - // pow((pow(10, (Y-d) / a) - c) / b, 1/g) = X + // pow((pow(10, (Y-d) / a) - c) / b, 1/g) = X case -7: Val = pow((pow(10.0, (R-Params[4]) / Params[1]) - Params[3]) / Params[2], 1.0 / Params[0]); break; - //Y = a * b^(c*X+d) + e + //Y = a * b^(c*X+d) + e case 8: Val = (Params[0] * pow(Params[1], Params[2] * R + Params[3]) + Params[4]); break; @@ -471,14 +471,14 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu // Y = (log((y-e) / a) / log(b) - d ) / c // a=0, b=1, c=2, d=3, e=4, case -8: - + disc = R - Params[4]; if (disc < 0) Val = 0; - else - Val = (log(disc / Params[0]) / log(Params[1]) - Params[3]) / Params[2]; + else + Val = (log(disc / Params[0]) / log(Params[1]) - Params[3]) / Params[2]; break; - // S-Shaped: (1 - (1-x)^1/g)^1/g + // S-Shaped: (1 - (1-x)^1/g)^1/g case 108: Val = pow(1.0 - pow(1 - R, 1/Params[0]), 1/Params[0]); break; @@ -501,7 +501,7 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu } // Evaluate a segmented funtion for a single value. Return -1 if no valid segment found . -// If fn type is 0, perform an interpolation on the table +// If fn type is 0, perform an interpolation on the table static cmsFloat64Number EvalSegmentedFn(const cmsToneCurve *g, cmsFloat64Number R) { @@ -519,10 +519,10 @@ cmsFloat64Number EvalSegmentedFn(const cmsToneCurve *g, cmsFloat64Number R) cmsFloat32Number Out; // Setup the table (TODO: clean that) - g ->SegInterp[i]-> Table = g ->Segments[i].SampledPoints; + g ->SegInterp[i]-> Table = g ->Segments[i].SampledPoints; g ->SegInterp[i] -> Interpolation.LerpFloat(&R1, &Out, g ->SegInterp[i]); - + return Out; } else @@ -563,17 +563,17 @@ int EntriesByGamma(cmsFloat64Number Gamma) // Create a segmented gamma, fill the table -cmsToneCurve* CMSEXPORT cmsBuildSegmentedToneCurve(cmsContext ContextID, +cmsToneCurve* CMSEXPORT cmsBuildSegmentedToneCurve(cmsContext ContextID, cmsInt32Number nSegments, const cmsCurveSegment Segments[]) { int i; cmsFloat64Number R, Val; cmsToneCurve* g; int nGridPoints = 4096; - + _cmsAssert(Segments != NULL); - // Optimizatin for identity curves. + // Optimizatin for identity curves. if (nSegments == 1 && Segments[0].Type == 1) { nGridPoints = EntriesByGamma(Segments[0].Params[0]); @@ -615,7 +615,7 @@ cmsToneCurve* CMSEXPORT cmsBuildTabulatedToneCurveFloat(cmsContext ContextID, cm // From zero to any Seg[1].x0 = 0; - Seg[1].x1 = 1.0; + Seg[1].x1 = 1.0; Seg[1].Type = 0; Seg[1].nGridPoints = nEntries; @@ -639,7 +639,7 @@ cmsToneCurve* CMSEXPORT cmsBuildParametricToneCurve(cmsContext ContextID, cmsInt _cmsAssert(Params != NULL); if (c == NULL) { - cmsSignalError(ContextID, cmsERROR_UNKNOWN_EXTENSION, "Invalid parametric curve type %d", Type); + cmsSignalError(ContextID, cmsERROR_UNKNOWN_EXTENSION, "Invalid parametric curve type %d", Type); return NULL; } @@ -668,27 +668,27 @@ cmsToneCurve* CMSEXPORT cmsBuildGamma(cmsContext ContextID, cmsFloat64Number Gam void CMSEXPORT cmsFreeToneCurve(cmsToneCurve* Curve) { cmsContext ContextID; - + if (Curve == NULL) return; ContextID = Curve ->InterpParams->ContextID; _cmsFreeInterpParams(Curve ->InterpParams); - + if (Curve -> Table16) _cmsFree(ContextID, Curve ->Table16); if (Curve ->Segments) { cmsUInt32Number i; - + for (i=0; i < Curve ->nSegments; i++) { if (Curve ->Segments[i].SampledPoints) { _cmsFree(ContextID, Curve ->Segments[i].SampledPoints); } - if (Curve ->SegInterp[i] != 0) + if (Curve ->SegInterp[i] != 0) _cmsFreeInterpParams(Curve->SegInterp[i]); } @@ -718,18 +718,18 @@ void CMSEXPORT cmsFreeToneCurveTriple(cmsToneCurve* Curve[3]) // Duplicate a gamma table cmsToneCurve* CMSEXPORT cmsDupToneCurve(const cmsToneCurve* In) -{ +{ if (In == NULL) return NULL; return AllocateToneCurveStruct(In ->InterpParams ->ContextID, In ->nEntries, In ->nSegments, In ->Segments, In ->Table16); } // Joins two curves for X and Y. Curves should be monotonic. -// We want to get +// We want to get // -// y = Y^-1(X(t)) +// y = Y^-1(X(t)) // -cmsToneCurve* CMSEXPORT cmsJoinToneCurve(cmsContext ContextID, +cmsToneCurve* CMSEXPORT cmsJoinToneCurve(cmsContext ContextID, const cmsToneCurve* X, const cmsToneCurve* Y, cmsUInt32Number nResultingPoints) { @@ -748,7 +748,7 @@ cmsToneCurve* CMSEXPORT cmsJoinToneCurve(cmsContext ContextID, Res = (cmsFloat32Number*) _cmsCalloc(ContextID, nResultingPoints, sizeof(cmsFloat32Number)); if (Res == NULL) goto Error; - + //Iterate for (i=0; i < nResultingPoints; i++) { @@ -759,7 +759,7 @@ cmsToneCurve* CMSEXPORT cmsJoinToneCurve(cmsContext ContextID, // Allocate space for output out = cmsBuildTabulatedToneCurveFloat(ContextID, nResultingPoints, Res); - + Error: if (Res != NULL) _cmsFree(ContextID, Res); @@ -770,25 +770,25 @@ Error: -// Get the surrounding nodes. This is tricky on non-monotonic tables +// Get the surrounding nodes. This is tricky on non-monotonic tables static int GetInterval(cmsFloat64Number In, const cmsUInt16Number LutTable[], const struct _cms_interp_struc* p) -{ +{ int i; int y0, y1; - + // A 1 point table is not allowed if (p -> Domain[0] < 1) return -1; - // Let's see if ascending or descending. + // Let's see if ascending or descending. if (LutTable[0] < LutTable[p ->Domain[0]]) { // Table is overall ascending for (i=p->Domain[0]-1; i >=0; --i) { - y0 = LutTable[i]; + y0 = LutTable[i]; y1 = LutTable[i+1]; - + if (y0 <= y1) { // Increasing if (In >= y0 && In <= y1) return i; } @@ -802,7 +802,7 @@ int GetInterval(cmsFloat64Number In, const cmsUInt16Number LutTable[], const str // Table is overall descending for (i=0; i < (int) p -> Domain[0]; i++) { - y0 = LutTable[i]; + y0 = LutTable[i]; y1 = LutTable[i+1]; if (y0 <= y1) { // Increasing @@ -825,18 +825,18 @@ cmsToneCurve* CMSEXPORT cmsReverseToneCurveEx(cmsInt32Number nResultSamples, con cmsFloat64Number a = 0, b = 0, y, x1, y1, x2, y2; int i, j; int Ascending; - + _cmsAssert(InCurve != NULL); // Try to reverse it analytically whatever possible if (InCurve ->nSegments == 1 && InCurve ->Segments[0].Type > 0 && InCurve -> Segments[0].Type <= 5) { - return cmsBuildParametricToneCurve(InCurve ->InterpParams->ContextID, - -(InCurve -> Segments[0].Type), + return cmsBuildParametricToneCurve(InCurve ->InterpParams->ContextID, + -(InCurve -> Segments[0].Type), InCurve -> Segments[0].Params); } - // Nope, reverse the table. + // Nope, reverse the table. out = cmsBuildTabulatedToneCurve16(InCurve ->InterpParams->ContextID, nResultSamples, NULL); if (out == NULL) return NULL; @@ -849,18 +849,18 @@ cmsToneCurve* CMSEXPORT cmsReverseToneCurveEx(cmsInt32Number nResultSamples, con y = (cmsFloat64Number) i * 65535.0 / (nResultSamples - 1); - // Find interval in which y is within. + // Find interval in which y is within. j = GetInterval(y, InCurve->Table16, InCurve->InterpParams); if (j >= 0) { // Get limits of interval - x1 = InCurve ->Table16[j]; + x1 = InCurve ->Table16[j]; x2 = InCurve ->Table16[j+1]; y1 = (cmsFloat64Number) (j * 65535.0) / (InCurve ->nEntries - 1); y2 = (cmsFloat64Number) ((j+1) * 65535.0 ) / (InCurve ->nEntries - 1); - + // If collapsed, then use any if (x1 == x2) { @@ -869,12 +869,12 @@ cmsToneCurve* CMSEXPORT cmsReverseToneCurveEx(cmsInt32Number nResultSamples, con } else { - // Interpolate + // Interpolate a = (y2 - y1) / (x2 - x1); b = y2 - a * x2; } } - + out ->Table16[i] = _cmsQuickSaturateWord(a* y + b); } @@ -910,7 +910,7 @@ cmsBool smooth2(cmsContext ContextID, cmsFloat32Number w[], cmsFloat32Number y[] c = (cmsFloat32Number*) _cmsCalloc(ContextID, MAX_NODES_IN_CURVE, sizeof(cmsFloat32Number)); d = (cmsFloat32Number*) _cmsCalloc(ContextID, MAX_NODES_IN_CURVE, sizeof(cmsFloat32Number)); e = (cmsFloat32Number*) _cmsCalloc(ContextID, MAX_NODES_IN_CURVE, sizeof(cmsFloat32Number)); - + if (c != NULL && d != NULL && e != NULL) { @@ -922,7 +922,7 @@ cmsBool smooth2(cmsContext ContextID, cmsFloat32Number w[], cmsFloat32Number y[] c[2] = (-4 * lambda - d[1] * c[1] * e[1]) / d[2]; e[2] = lambda / d[2]; z[2] = w[2] * y[2] - c[1] * z[1]; - + for (i = 3; i < m - 1; i++) { i1 = i - 1; i2 = i - 2; d[i]= w[i] + 6 * lambda - c[i1] * c[i1] * d[i1] - e[i2] * e[i2] * d[i2]; @@ -930,18 +930,18 @@ cmsBool smooth2(cmsContext ContextID, cmsFloat32Number w[], cmsFloat32Number y[] e[i] = lambda / d[i]; z[i] = w[i] * y[i] - c[i1] * z[i1] - e[i2] * z[i2]; } - + i1 = m - 2; i2 = m - 3; - + d[m - 1] = w[m - 1] + 5 * lambda -c[i1] * c[i1] * d[i1] - e[i2] * e[i2] * d[i2]; c[m - 1] = (-2 * lambda - d[i1] * c[i1] * e[i1]) / d[m - 1]; z[m - 1] = w[m - 1] * y[m - 1] - c[i1] * z[i1] - e[i2] * z[i2]; i1 = m - 1; i2 = m - 2; - + d[m] = w[m] + lambda - c[i1] * c[i1] * d[i1] - e[i2] * e[i2] * d[i2]; z[m] = (w[m] * y[m] - c[i1] * z[i1] - e[i2] * z[i2]) / d[m]; z[m - 1] = z[m - 1] / d[m - 1] - c[m - 1] * z[m]; - + for (i = m - 2; 1<= i; i--) z[i] = z[i] / d[i] - c[i] * z[i + 1] - e[i] * z[i + 2]; @@ -956,7 +956,7 @@ cmsBool smooth2(cmsContext ContextID, cmsFloat32Number w[], cmsFloat32Number y[] return st; } -// Smooths a curve sampled at regular intervals. +// Smooths a curve sampled at regular intervals. cmsBool CMSEXPORT cmsSmoothToneCurve(cmsToneCurve* Tab, cmsFloat64Number lambda) { cmsFloat32Number w[MAX_NODES_IN_CURVE], y[MAX_NODES_IN_CURVE], z[MAX_NODES_IN_CURVE]; @@ -1034,14 +1034,14 @@ cmsBool CMSEXPORT cmsIsToneCurveMonotonic(const cmsToneCurve* t) cmsBool lDescending; _cmsAssert(t != NULL); - + // Degenerated curves are monotonic? Ok, let's pass them n = t ->nEntries; if (n < 2) return TRUE; // Curve direction - lDescending = cmsIsToneCurveDescending(t); - + lDescending = cmsIsToneCurveDescending(t); + if (lDescending) { last = t ->Table16[0]; @@ -1060,7 +1060,7 @@ cmsBool CMSEXPORT cmsIsToneCurveMonotonic(const cmsToneCurve* t) last = t ->Table16[n-1]; for (i = n-2; i >= 0; --i) { - + if (t ->Table16[i] - last > 2) return FALSE; else @@ -1106,10 +1106,10 @@ cmsFloat32Number CMSEXPORT cmsEvalToneCurveFloat(const cmsToneCurve* Curve, cmsF if (Curve ->nSegments == 0) { cmsUInt16Number In, Out; - + In = (cmsUInt16Number) _cmsQuickSaturateWord(v * 65535.0); Out = cmsEvalToneCurve16(Curve, In); - + return (cmsFloat32Number) (Out / 65535.0); } @@ -1129,21 +1129,21 @@ cmsUInt16Number CMSEXPORT cmsEvalToneCurve16(const cmsToneCurve* Curve, cmsUInt1 // Least squares fitting. -// A mathematical procedure for finding the best-fitting curve to a given set of points by -// minimizing the sum of the squares of the offsets ("the residuals") of the points from the curve. -// The sum of the squares of the offsets is used instead of the offset absolute values because -// this allows the residuals to be treated as a continuous differentiable quantity. +// A mathematical procedure for finding the best-fitting curve to a given set of points by +// minimizing the sum of the squares of the offsets ("the residuals") of the points from the curve. +// The sum of the squares of the offsets is used instead of the offset absolute values because +// this allows the residuals to be treated as a continuous differentiable quantity. // // y = f(x) = x ^ g // // R = (yi - (xi^g)) // R2 = (yi - (xi^g))2 // SUM R2 = SUM (yi - (xi^g))2 -// -// dR2/dg = -2 SUM x^g log(x)(y - x^g) -// solving for dR2/dg = 0 -// -// g = 1/n * SUM(log(y) / log(x)) +// +// dR2/dg = -2 SUM x^g log(x)(y - x^g) +// solving for dR2/dg = 0 +// +// g = 1/n * SUM(log(y) / log(x)) cmsFloat64Number CMSEXPORT cmsEstimateGamma(const cmsToneCurve* t, cmsFloat64Number Precision) { @@ -1155,13 +1155,13 @@ cmsFloat64Number CMSEXPORT cmsEstimateGamma(const cmsToneCurve* t, cmsFloat64Num sum = sum2 = n = 0; - // Excluding endpoints + // Excluding endpoints for (i=1; i < (MAX_NODES_IN_CURVE-1); i++) { x = (cmsFloat64Number) i / (MAX_NODES_IN_CURVE-1); y = (cmsFloat64Number) cmsEvalToneCurveFloat(t, (cmsFloat32Number) x); - // Avoid 7% on lower part to prevent + // Avoid 7% on lower part to prevent // artifacts due to linear ramps if (y > 0. && y < 1. && x > 0.07) { |