colorspace Converting between RGB, YUV, HSV, CIE Lab

/** * @file colorspace.c * @author Pascal Getreuer 2005-2010 <getreuer@gmail.com> * * == 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 num S[3] = {173, 0.8, 0.5}; num 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 num R = 0.85, G = 0.32, B = 0.5; num 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(num *Y, num *U, num *V, num R, num G, num B) * - Rgb2Ycbcr(num *Y, num *Cb, num *Cr, num R, num G, num B) * - Rgb2Jpegycbcr(num *Y, num *Cb, num *Cr, num R, num G, num B) * - Rgb2Ypbpr(num *Y, num *Pb, num *Pr, num R, num G, num B) * - Rgb2Ydbdr(num *Y, num *Db, num *Dr, num R, num G, num B) * - Rgb2Yiq(num *Y, num *I, num *Q, num R, num G, num B) * - Rgb2Hsv(num *H, num *S, num *V, num R, num G, num B) * - Rgb2Hsl(num *H, num *S, num *L, num R, num G, num B) * - Rgb2Hsi(num *H, num *S, num *I, num R, num G, num B) * - Rgb2Xyz(num *X, num *Y, num *Z, num R, num G, num B) * - Xyz2Lab(num *L, num *a, num *b, num X, num Y, num Z) * - Xyz2Luv(num *L, num *u, num *v, num X, num Y, num Z) * - Xyz2Lch(num *L, num *C, num *h, num X, num Y, num Z) * - Xyz2Cat02lms(num *L, num *M, num *S, num X, num Y, num Z) * - Rgb2Lab(num *L, num *a, num *b, num R, num G, num B) * - Rgb2Luv(num *L, num *u, num *v, num R, num G, num B) * - Rgb2Lch(num *L, num *C, num *h, num R, num G, num B) * - Rgb2Cat02lms(num *L, num *M, num *S, num R, num G, num 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 <math.h> #include <stdio.h> #include <string.h> #include <ctype.h> #include "colorspace.h" #ifdef MATLAB_MEX_FILE #include "mex.h" #endif /** @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_S