/** * @file colorspace.c * @author Pascal Getreuer 2005-2010 * * == Summary == * This file implements routines for color transformations between the spaces * sRGB, Y'UV, Y'CbCr, Y'PbPr, Y'DbDr, Y'IQ, HSV, HSL, HSI, CIEXYZ, CIELAB, * CIELUV, CIELCH, and CIECAT02 LMS. * * == Usage == * First call GetColorTransform, specifying the source and destination color * spaces as "dest<-src" or "src->dest". Then call ApplyColorTransform to * perform the transform: @code double S[3] = {173, 0.8, 0.5}; double D[3]; colortransform Trans; if(!(GetColorTransform(&Trans, "HSI -> Lab"))) { printf("Invalid syntax or unknown color space\n"); return; } ApplyColorTransform(Trans, &D[0], &D[1], &D[2], S[0], S[1], S[2]); @endcode * "num" is a typedef defined at the beginning of colorspace.h that may be set * to either double or float, depending on the application. * * Specific transformation routines can also be called directly. The following * converts an sRGB color to CIELAB and then back to sRGB: @code double R = 0.85, G = 0.32, B = 0.5; double L, a, b; Rgb2Lab(&L, &a, &b, R, G, B); Lab2Rgb(&R, &G, &B, L, a, b); @endcode * Generally, the calling syntax is @code Foo2Bar(&B0, &B1, &B2, F0, F1, F2); @endcode * where (F0,F1,F2) are the coordinates of a color in space "Foo" and * (B0,B1,B2) are the transformed coordinates in space "Bar." For any * transformation routine, its inverse has the sytax @code Bar2Foo(&F0, &F1, &F2, B0, B1, B2); @endcode * * The conversion routines are consistently named with the first letter of a * color space capitalized with following letters in lower case and omitting * prime symbols. For example, "Rgb2Ydbdr" converts sRGB to Y'DbDr. For * any transformation routine Foo2Bar, its inverse is Bar2Foo. * * All transformations assume a two degree observer angle and a D65 illuminant. * The white point can be changed by modifying the WHITEPOINT_X, WHITEPOINT_Y, * WHITEPOINT_Z definitions at the beginning of colorspace.h. * * == List of transformation routines == * - Rgb2Yuv(double *Y, double *U, double *V, double R, double G, double B) * - Rgb2Ycbcr(double *Y, double *Cb, double *Cr, double R, double G, double B) * - Rgb2Jpegycbcr(double *Y, double *Cb, double *Cr, double R, double G, double B) * - Rgb2Ypbpr(double *Y, double *Pb, double *Pr, double R, double G, double B) * - Rgb2Ydbdr(double *Y, double *Db, double *Dr, double R, double G, double B) * - Rgb2Yiq(double *Y, double *I, double *Q, double R, double G, double B) * - Rgb2Hsv(double *H, double *S, double *V, double R, double G, double B) * - Rgb2Hsl(double *H, double *S, double *L, double R, double G, double B) * - Rgb2Hsi(double *H, double *S, double *I, double R, double G, double B) * - Rgb2Xyz(double *X, double *Y, double *Z, double R, double G, double B) * - Xyz2Lab(double *L, double *a, double *b, double X, double Y, double Z) * - Xyz2Luv(double *L, double *u, double *v, double X, double Y, double Z) * - Xyz2Lch(double *L, double *C, double *h, double X, double Y, double Z) * - Xyz2Cat02lms(double *L, double *M, double *S, double X, double Y, double Z) * - Rgb2Lab(double *L, double *a, double *b, double R, double G, double B) * - Rgb2Luv(double *L, double *u, double *v, double R, double G, double B) * - Rgb2Lch(double *L, double *C, double *h, double R, double G, double B) * - Rgb2Cat02lms(double *L, double *M, double *S, double R, double G, double B) * (Similarly for the inverse transformations.) * * It is possible to transform between two arbitrary color spaces by first * transforming from the source space to sRGB and then transforming from * sRGB to the desired destination space. For transformations between CIE * color spaces, it is convenient to use XYZ as the intermediate space. This * is the strategy used by GetColorTransform and ApplyColorTransform. * * == References == * The definitions of these spaces and the many of the transformation formulas * can be found in * * Poynton, "Frequently Asked Questions About Gamma" * http://www.poynton.com/notes/colour_and_gamma/GammaFAQ.html * * Poynton, "Frequently Asked Questions About Color" * http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html * * and Wikipedia articles * http://en.wikipedia.org/wiki/SRGB * http://en.wikipedia.org/wiki/YUV * http://en.wikipedia.org/wiki/YCbCr * http://en.wikipedia.org/wiki/YPbPr * http://en.wikipedia.org/wiki/YDbDr * http://en.wikipedia.org/wiki/YIQ * http://en.wikipedia.org/wiki/HSL_and_HSV * http://en.wikipedia.org/wiki/CIE_1931_color_space * http://en.wikipedia.org/wiki/Lab_color_space * http://en.wikipedia.org/wiki/CIELUV_color_space * http://en.wikipedia.org/wiki/LMS_color_space * * == License (BSD) == * Copyright (c) 2005-2010, Pascal Getreuer * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ #include #include #include #include #include "gtkmm2ext/colorspace.h" namespace Gtkmm2ext { /** @brief Min of A and B */ #define MIN(A,B) (((A) <= (B)) ? (A) : (B)) /** @brief Max of A and B */ #define MAX(A,B) (((A) >= (B)) ? (A) : (B)) /** @brief Min of A, B, and C */ #define MIN3(A,B,C) (((A) <= (B)) ? MIN(A,C) : MIN(B,C)) /** @brief Max of A, B, and C */ #define MAX3(A,B,C) (((A) >= (B)) ? MAX(A,C) : MAX(B,C)) #ifndef M_PI /** @brief The constant pi */ #define M_PI 3.14159265358979323846264338327950288 #endif /** * @brief sRGB gamma correction, transforms R to R' * http://en.wikipedia.org/wiki/SRGB */ #define GAMMACORRECTION(t) \ (((t) <= 0.0031306684425005883) ? \ (12.92*(t)) : (1.055*pow((t), 0.416666666666666667) - 0.055)) /** * @brief Inverse sRGB gamma correction, transforms R' to R */ #define INVGAMMACORRECTION(t) \ (((t) <= 0.0404482362771076) ? \ ((t)/12.92) : pow(((t) + 0.055)/1.055, 2.4)) /** * @brief CIE L*a*b* f function (used to convert XYZ to L*a*b*) * http://en.wikipedia.org/wiki/Lab_color_space */ #define LABF(t) \ ((t >= 8.85645167903563082e-3) ? \ pow(t,0.333333333333333) : (841.0/108.0)*(t) + (4.0/29.0)) /** * @brief CIE L*a*b* inverse f function * http://en.wikipedia.org/wiki/Lab_color_space */ #define LABINVF(t) \ ((t >= 0.206896551724137931) ? \ ((t)*(t)*(t)) : (108.0/841.0)*((t) - (4.0/29.0))) /** @brief u'v' coordinates of the white point for CIE Lu*v* */ #define WHITEPOINT_U ((4*WHITEPOINT_X) \ /(WHITEPOINT_X + 15*WHITEPOINT_Y + 3*WHITEPOINT_Z)) #define WHITEPOINT_V ((9*WHITEPOINT_Y) \ /(WHITEPOINT_X + 15*WHITEPOINT_Y + 3*WHITEPOINT_Z)) /** @brief Enumeration of the supported color spaces */ #define UNKNOWN_SPACE 0 #define RGB_SPACE 1 #define YUV_SPACE 2 #define YCBCR_SPACE 3 #define JPEGYCBCR_SPACE 4 #define YPBPR_SPACE 5 #define YDBDR_SPACE 6 #define YIQ_SPACE 7 #define HSV_SPACE 8 #define HSL_SPACE 9 #define HSI_SPACE 10 #define XYZ_SPACE 11 #define LAB_SPACE 12 #define LUV_SPACE 13 #define LCH_SPACE 14 #define CAT02LMS_SPACE 15 #define NUM_TRANSFORM_PAIRS 18 /* * == Linear color transformations == * * The following routines implement transformations between sRGB and * the linearly-related color spaces Y'UV, Y'PbPr, Y'DbDr, and Y'IQ. */ /** * @brief Convert sRGB to NTSC/PAL Y'UV Luma + Chroma * * @param Y, U, V pointers to hold the result * @param R, G, B the input sRGB values * * Wikipedia: http://en.wikipedia.org/wiki/YUV */ void Rgb2Yuv(double *Y, double *U, double *V, double R, double G, double B) { *Y = (double)( 0.299*R + 0.587*G + 0.114*B); *U = (double)(-0.147*R - 0.289*G + 0.436*B); *V = (double)( 0.615*R - 0.515*G - 0.100*B); } /** * @brief Convert NTSC/PAL Y'UV to sRGB * * @param R, G, B pointers to hold the result * @param Y, U, V the input YUV values */ void Yuv2Rgb(double *R, double *G, double *B, double Y, double U, double V) { *R = (double)(Y - 3.945707070708279e-05*U + 1.1398279671717170825*V); *G = (double)(Y - 0.3946101641414141437*U - 0.5805003156565656797*V); *B = (double)(Y + 2.0319996843434342537*U - 4.813762626262513e-04*V); } /** @brief sRGB to Y'CbCr Luma + Chroma */ void Rgb2Ycbcr(double *Y, double *Cb, double *Cr, double R, double G, double B) { *Y = (double)( 65.481*R + 128.553*G + 24.966*B + 16); *Cb = (double)(-37.797*R - 74.203*G + 112.0 *B + 128); *Cr = (double)(112.0 *R - 93.786*G - 18.214*B + 128); } /** @brief Y'CbCr to sRGB */ void Ycbcr2Rgb(double *R, double *G, double *B, double Y, double Cr, double Cb) { Y -= 16; Cb -= 128; Cr -= 128; *R = (double)(0.00456621004566210107*Y + 1.1808799897946415e-09*Cr + 0.00625892896994393634*Cb); *G = (double)(0.00456621004566210107*Y - 0.00153632368604490212*Cr - 0.00318811094965570701*Cb); *B = (double)(0.00456621004566210107*Y + 0.00791071623355474145*Cr + 1.1977497040190077e-08*Cb); } /** @brief sRGB to JPEG-Y'CbCr Luma + Chroma */ void Rgb2Jpegycbcr(double *Y, double *Cb, double *Cr, double R, double G, double B) { Rgb2Ypbpr(Y, Cb, Cr, R, G, B); *Cb += (double)0.5; *Cr += (double)0.5; } /** @brief JPEG-Y'CbCr to sRGB */ void Jpegycbcr2Rgb(double *R, double *G, double *B, double Y, double Cb, double Cr) { Cb -= (double)0.5; Cr -= (double)0.5; Ypbpr2Rgb(R, G, B, Y, Cb, Cr); } /** @brief sRGB to Y'PbPr Luma (ITU-R BT.601) + Chroma */ void Rgb2Ypbpr(double *Y, double *Pb, double *Pr, double R, double G, double B) { *Y = (double)( 0.299 *R + 0.587 *G + 0.114 *B); *Pb = (double)(-0.1687367*R - 0.331264*G + 0.5 *B); *Pr = (double)( 0.5 *R - 0.418688*G - 0.081312*B); } /** @brief Y'PbPr to sRGB */ void Ypbpr2Rgb(double *R, double *G, double *B, double Y, double Pb, double Pr) { *R = (double)(0.99999999999914679361*Y - 1.2188941887145875e-06*Pb + 1.4019995886561440468*Pr); *G = (double)(0.99999975910502514331*Y - 0.34413567816504303521*Pb - 0.71413649331646789076*Pr); *B = (double)(1.00000124040004623180*Y + 1.77200006607230409200*Pb + 2.1453384174593273e-06*Pr); } /** @brief sRGB to SECAM Y'DbDr Luma + Chroma */ void Rgb2Ydbdr(double *Y, double *Db, double *Dr, double R, double G, double B) { *Y = (double)( 0.299*R + 0.587*G + 0.114*B); *Db = (double)(-0.450*R - 0.883*G + 1.333*B); *Dr = (double)(-1.333*R + 1.116*G + 0.217*B); } /** @brief SECAM Y'DbDr to sRGB */ void Ydbdr2Rgb(double *R, double *G, double *B, double Y, double Db, double Dr) { *R = (double)(Y + 9.2303716147657e-05*Db - 0.52591263066186533*Dr); *G = (double)(Y - 0.12913289889050927*Db + 0.26789932820759876*Dr); *B = (double)(Y + 0.66467905997895482*Db - 7.9202543533108e-05*Dr); } /** @brief sRGB to NTSC YIQ */ void Rgb2Yiq(double *Y, double *I, double *Q, double R, double G, double B) { *Y = (double)(0.299 *R + 0.587 *G + 0.114 *B); *I = (double)(0.595716*R - 0.274453*G - 0.321263*B); *Q = (double)(0.211456*R - 0.522591*G + 0.311135*B); } /** @brief Convert NTSC YIQ to sRGB */ void Yiq2Rgb(double *R, double *G, double *B, double Y, double I, double Q) { *R = (double)(Y + 0.9562957197589482261*I + 0.6210244164652610754*Q); *G = (double)(Y - 0.2721220993185104464*I - 0.6473805968256950427*Q); *B = (double)(Y - 1.1069890167364901945*I + 1.7046149983646481374*Q); } /* * == Hue Saturation Value/Lightness/Intensity color transformations == * * The following routines implement transformations between sRGB and * color spaces HSV, HSL, and HSI. */ /** * @brief Convert an sRGB color to Hue-Saturation-Value (HSV) * * @param H, S, V pointers to hold the result * @param R, G, B the input sRGB values scaled in [0,1] * * This routine transforms from sRGB to the hexcone HSV color space. The * sRGB values are assumed to be between 0 and 1. The output values are * H = hexagonal hue angle (0 <= H < 360), * S = C/V (0 <= S <= 1), * V = max(R',G',B') (0 <= V <= 1), * where C = max(R',G',B') - min(R',G',B'). The inverse color transformation * is given by Hsv2Rgb. * * Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV */ void Rgb2Hsv(double *H, double *S, double *V, double R, double G, double B) { double Max = MAX3(R, G, B); double Min = MIN3(R, G, B); double C = Max - Min; *V = Max; if(C > 0) { if(Max == R) { *H = (G - B) / C; if(G < B) *H += 6; } else if(Max == G) *H = 2 + (B - R) / C; else *H = 4 + (R - G) / C; *H *= 60; *S = C / Max; } else *H = *S = 0; } /** * @brief Convert a Hue-Saturation-Value (HSV) color to sRGB * * @param R, G, B pointers to hold the result * @param H, S, V the input HSV values * * The input values are assumed to be scaled as * 0 <= H < 360, * 0 <= S <= 1, * 0 <= V <= 1. * The output sRGB values are scaled between 0 and 1. This is the inverse * transformation of Rgb2Hsv. * * Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV */ void Hsv2Rgb(double *R, double *G, double *B, double H, double S, double V) { double C = S * V; double Min = V - C; double X; H -= 360*floor(H/360); H /= 60; X = C*(1 - fabs(H - 2*floor(H/2) - 1)); switch((int)H) { case 0: *R = Min + C; *G = Min + X; *B = Min; break; case 1: *R = Min + X; *G = Min + C; *B = Min; break; case 2: *R = Min; *G = Min + C; *B = Min + X; break; case 3: *R = Min; *G = Min + X; *B = Min + C; break; case 4: *R = Min + X; *G = Min; *B = Min + C; break; case 5: *R = Min + C; *G = Min; *B = Min + X; break; default: *R = *G = *B = 0; } } /** * @brief Convert an sRGB color to Hue-Saturation-Lightness (HSL) * * @param H, S, L pointers to hold the result * @param R, G, B the input sRGB values scaled in [0,1] * * This routine transforms from sRGB to the double hexcone HSL color space * The sRGB values are assumed to be between 0 and 1. The outputs are * H = hexagonal hue angle (0 <= H < 360), * S = { C/(2L) if L <= 1/2 (0 <= S <= 1), * { C/(2 - 2L) if L > 1/2 * L = (max(R',G',B') + min(R',G',B'))/2 (0 <= L <= 1), * where C = max(R',G',B') - min(R',G',B'). The inverse color transformation * is given by Hsl2Rgb. * * Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV */ void Rgb2Hsl(double *H, double *S, double *L, double R, double G, double B) { double Max = MAX3(R, G, B); double Min = MIN3(R, G, B); double C = Max - Min; *L = (Max + Min)/2; if(C > 0) { if(Max == R) { *H = (G - B) / C; if(G < B) *H += 6; } else if(Max == G) *H = 2 + (B - R) / C; else *H = 4 + (R - G) / C; *H *= 60; *S = (*L <= 0.5) ? (C/(2*(*L))) : (C/(2 - 2*(*L))); } else *H = *S = 0; } /** * @brief Convert a Hue-Saturation-Lightness (HSL) color to sRGB * * @param R, G, B pointers to hold the result * @param H, S, L the input HSL values * * The input values are assumed to be scaled as * 0 <= H < 360, * 0 <= S <= 1, * 0 <= L <= 1. * The output sRGB values are scaled between 0 and 1. This is the inverse * transformation of Rgb2Hsl. * * Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV */ void Hsl2Rgb(double *R, double *G, double *B, double H, double S, double L) { double C = (L <= 0.5) ? (2*L*S) : ((2 - 2*L)*S); double Min = L - 0.5*C; double X; H -= 360*floor(H/360); H /= 60; X = C*(1 - fabs(H - 2*floor(H/2) - 1)); switch((int)H) { case 0: *R = Min + C; *G = Min + X; *B = Min; break; case 1: *R = Min + X; *G = Min + C; *B = Min; break; case 2: *R = Min; *G = Min + C; *B = Min + X; break; case 3: *R = Min; *G = Min + X; *B = Min + C; break; case 4: *R = Min + X; *G = Min; *B = Min + C; break; case 5: *R = Min + C; *G = Min; *B = Min + X; break; default: *R = *G = *B = 0; } } /** * @brief Convert an sRGB color to Hue-Saturation-Intensity (HSI) * * @param H, S, I pointers to hold the result * @param R, G, B the input sRGB values scaled in [0,1] * * This routine transforms from sRGB to the cylindrical HSI color space. The * sRGB values are assumed to be between 0 and 1. The output values are * H = polar hue angle (0 <= H < 360), * S = 1 - min(R',G',B')/I (0 <= S <= 1), * I = (R'+G'+B')/3 (0 <= I <= 1). * The inverse color transformation is given by Hsi2Rgb. * * Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV */ void Rgb2Hsi(double *H, double *S, double *I, double R, double G, double B) { double alpha = 0.5*(2*R - G - B); double beta = 0.866025403784439*(G - B); *I = (R + G + B)/3; if(*I > 0) { *S = 1 - MIN3(R,G,B) / *I; *H = atan2(beta, alpha)*(180/M_PI); if(*H < 0) *H += 360; } else *H = *S = 0; } /** * @brief Convert a Hue-Saturation-Intesity (HSI) color to sRGB * * @param R, G, B pointers to hold the result * @param H, S, I the input HSI values * * The input values are assumed to be scaled as * 0 <= H < 360, * 0 <= S <= 1, * 0 <= I <= 1. * The output sRGB values are scaled between 0 and 1. This is the inverse * transformation of Rgb2Hsi. * * Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV */ void Hsi2Rgb(double *R, double *G, double *B, double H, double S, double I) { H -= 360*floor(H/360); if(H < 120) { *B = I*(1 - S); *R = I*(1 + S*cos(H*(M_PI/180))/cos((60 - H)*(M_PI/180))); *G = 3*I - *R - *B; } else if(H < 240) { H -= 120; *R = I*(1 - S); *G = I*(1 + S*cos(H*(M_PI/180))/cos((60 - H)*(M_PI/180))); *B = 3*I - *R - *G; } else { H -= 240; *G = I*(1 - S); *B = I*(1 + S*cos(H*(M_PI/180))/cos((60 - H)*(M_PI/180))); *R = 3*I - *G - *B; } } /* * == CIE color transformations == * * The following routines implement transformations between sRGB and * the CIE color spaces XYZ, L*a*b, L*u*v*, and L*C*H*. These * transforms assume a 2 degree observer angle and a D65 illuminant. */ /** * @brief Transform sRGB to CIE XYZ with the D65 white point * * @param X, Y, Z pointers to hold the result * @param R, G, B the input sRGB values * * Poynton, "Frequently Asked Questions About Color," page 10 * Wikipedia: http://en.wikipedia.org/wiki/SRGB * Wikipedia: http://en.wikipedia.org/wiki/CIE_1931_color_space */ void Rgb2Xyz(double *X, double *Y, double *Z, double R, double G, double B) { R = INVGAMMACORRECTION(R); G = INVGAMMACORRECTION(G); B = INVGAMMACORRECTION(B); *X = (double)(0.4123955889674142161*R + 0.3575834307637148171*G + 0.1804926473817015735*B); *Y = (double)(0.2125862307855955516*R + 0.7151703037034108499*G + 0.07220049864333622685*B); *Z = (double)(0.01929721549174694484*R + 0.1191838645808485318*G + 0.9504971251315797660*B); } /** * @brief Transform CIE XYZ to sRGB with the D65 white point * * @param R, G, B pointers to hold the result * @param X, Y, Z the input XYZ values * * Official sRGB specification (IEC 61966-2-1:1999) * Poynton, "Frequently Asked Questions About Color," page 10 * Wikipedia: http://en.wikipedia.org/wiki/SRGB * Wikipedia: http://en.wikipedia.org/wiki/CIE_1931_color_space */ void Xyz2Rgb(double *R, double *G, double *B, double X, double Y, double Z) { double R1, B1, G1, Min; R1 = (double)( 3.2406*X - 1.5372*Y - 0.4986*Z); G1 = (double)(-0.9689*X + 1.8758*Y + 0.0415*Z); B1 = (double)( 0.0557*X - 0.2040*Y + 1.0570*Z); Min = MIN3(R1, G1, B1); /* Force nonnegative values so that gamma correction is well-defined. */ if(Min < 0) { R1 -= Min; G1 -= Min; B1 -= Min; } /* Transform from RGB to R'G'B' */ *R = GAMMACORRECTION(R1); *G = GAMMACORRECTION(G1); *B = GAMMACORRECTION(B1); } /** * Convert CIE XYZ to CIE L*a*b* (CIELAB) with the D65 white point * * @param L, a, b pointers to hold the result * @param X, Y, Z the input XYZ values * * Wikipedia: http://en.wikipedia.org/wiki/Lab_color_space */ void Xyz2Lab(double *L, double *a, double *b, double X, double Y, double Z) { X /= WHITEPOINT_X; Y /= WHITEPOINT_Y; Z /= WHITEPOINT_Z; X = LABF(X); Y = LABF(Y); Z = LABF(Z); *L = 116*Y - 16; *a = 500*(X - Y); *b = 200*(Y - Z); } /** * Convert CIE L*a*b* (CIELAB) to CIE XYZ with the D65 white point * * @param X, Y, Z pointers to hold the result * @param L, a, b the input L*a*b* values * * Wikipedia: http://en.wikipedia.org/wiki/Lab_color_space */ void Lab2Xyz(double *X, double *Y, double *Z, double L, double a, double b) { L = (L + 16)/116; a = L + a/500; b = L - b/200; *X = WHITEPOINT_X*LABINVF(a); *Y = WHITEPOINT_Y*LABINVF(L); *Z = WHITEPOINT_Z*LABINVF(b); } /** * Convert CIE XYZ to CIE L*u*v* (CIELUV) with the D65 white point * * @param L, u, v pointers to hold the result * @param X, Y, Z the input XYZ values * * Wikipedia: http://en.wikipedia.org/wiki/CIELUV_color_space */ void Xyz2Luv(double *L, double *u, double *v, double X, double Y, double Z) { double u1, v1, Denom; if((Denom = X + 15*Y + 3*Z) > 0) { u1 = (4*X) / Denom; v1 = (9*Y) / Denom; } else u1 = v1 = 0; Y /= WHITEPOINT_Y; Y = LABF(Y); *L = 116*Y - 16; *u = 13*(*L)*(u1 - WHITEPOINT_U); *v = 13*(*L)*(v1 - WHITEPOINT_V); } /** * Convert CIE L*u*v* (CIELUV) to CIE XYZ with the D65 white point * * @param X, Y, Z pointers to hold the result * @param L, u, v the input L*u*v* values * * Wikipedia: http://en.wikipedia.org/wiki/CIELUV_color_space */ void Luv2Xyz(double *X, double *Y, double *Z, double L, double u, double v) { *Y = (L + 16)/116; *Y = WHITEPOINT_Y*LABINVF(*Y); if(L != 0) { u /= L; v /= L; } u = u/13 + WHITEPOINT_U; v = v/13 + WHITEPOINT_V; *X = (*Y) * ((9*u)/(4*v)); *Z = (*Y) * ((3 - 0.75*u)/v - 5); } /** * Convert CIE XYZ to CIE L*C*H* with the D65 white point * * @param L, C, H pointers to hold the result * @param X, Y, Z the input XYZ values * * CIE L*C*H* is related to CIE L*a*b* by * a* = C* cos(H* pi/180), * b* = C* sin(H* pi/180). */ void Xyz2Lch(double *L, double *C, double *H, double X, double Y, double Z) { double a, b; Xyz2Lab(L, &a, &b, X, Y, Z); *C = sqrt(a*a + b*b); *H = atan2(b, a)*180.0/M_PI; if(*H < 0) *H += 360; } /** * Convert CIE L*C*H* to CIE XYZ with the D65 white point * * @param X, Y, Z pointers to hold the result * @param L, C, H the input L*C*H* values */ void Lch2Xyz(double *X, double *Y, double *Z, double L, double C, double H) { double a = C * cos(H*(M_PI/180.0)); double b = C * sin(H*(M_PI/180.0)); Lab2Xyz(X, Y, Z, L, a, b); } /** @brief XYZ to CAT02 LMS */ void Xyz2Cat02lms(double *L, double *M, double *S, double X, double Y, double Z) { *L = (double)( 0.7328*X + 0.4296*Y - 0.1624*Z); *M = (double)(-0.7036*X + 1.6975*Y + 0.0061*Z); *S = (double)( 0.0030*X + 0.0136*Y + 0.9834*Z); } /** @brief CAT02 LMS to XYZ */ void Cat02lms2Xyz(double *X, double *Y, double *Z, double L, double M, double S) { *X = (double)( 1.096123820835514*L - 0.278869000218287*M + 0.182745179382773*S); *Y = (double)( 0.454369041975359*L + 0.473533154307412*M + 0.072097803717229*S); *Z = (double)(-0.009627608738429*L - 0.005698031216113*M + 1.015325639954543*S); } /* * == Glue functions for multi-stage transforms == */ void Rgb2Lab(double *L, double *a, double *b, double R, double G, double B) { double X, Y, Z; Rgb2Xyz(&X, &Y, &Z, R, G, B); Xyz2Lab(L, a, b, X, Y, Z); } void Lab2Rgb(double *R, double *G, double *B, double L, double a, double b) { double X, Y, Z; Lab2Xyz(&X, &Y, &Z, L, a, b); Xyz2Rgb(R, G, B, X, Y, Z); } void Rgb2Luv(double *L, double *u, double *v, double R, double G, double B) { double X, Y, Z; Rgb2Xyz(&X, &Y, &Z, R, G, B); Xyz2Luv(L, u, v, X, Y, Z); } void Luv2Rgb(double *R, double *G, double *B, double L, double u, double v) { double X, Y, Z; Luv2Xyz(&X, &Y, &Z, L, u, v); Xyz2Rgb(R, G, B, X, Y, Z); } void Rgb2Lch(double *L, double *C, double *H, double R, double G, double B) { double X, Y, Z; Rgb2Xyz(&X, &Y, &Z, R, G, B); Xyz2Lch(L, C, H, X, Y, Z); } void Lch2Rgb(double *R, double *G, double *B, double L, double C, double H) { double X, Y, Z; Lch2Xyz(&X, &Y, &Z, L, C, H); Xyz2Rgb(R, G, B, X, Y, Z); } void Rgb2Cat02lms(double *L, double *M, double *S, double R, double G, double B) { double X, Y, Z; Rgb2Xyz(&X, &Y, &Z, R, G, B); Xyz2Cat02lms(L, M, S, X, Y, Z); } void Cat02lms2Rgb(double *R, double *G, double *B, double L, double M, double S) { double X, Y, Z; Cat02lms2Xyz(&X, &Y, &Z, L, M, S); Xyz2Rgb(R, G, B, X, Y, Z); } } /* namespace */