1 /* 2 * cmyk.h 3 * 4 * Copyright (C) 2017-2018, D. R. Commander. 5 * For conditions of distribution and use, see the accompanying README.ijg 6 * file. 7 * 8 * This file contains convenience functions for performing quick & dirty 9 * CMYK<->RGB conversion. This algorithm is suitable for testing purposes 10 * only. Properly converting between CMYK and RGB requires a color management 11 * system. 12 */ 13 14 #ifndef CMYK_H 15 #define CMYK_H 16 17 #include <jinclude.h> 18 #define JPEG_INTERNALS 19 #include <jpeglib.h> 20 #include "jconfigint.h" 21 22 23 /* Fully reversible */ 24 25 INLINE 26 LOCAL(void) 27 rgb_to_cmyk(JSAMPLE r, JSAMPLE g, JSAMPLE b, JSAMPLE *c, JSAMPLE *m, 28 JSAMPLE *y, JSAMPLE *k) 29 { 30 double ctmp = 1.0 - ((double)r / 255.0); 31 double mtmp = 1.0 - ((double)g / 255.0); 32 double ytmp = 1.0 - ((double)b / 255.0); 33 double ktmp = MIN(MIN(ctmp, mtmp), ytmp); 34 35 if (ktmp == 1.0) ctmp = mtmp = ytmp = 0.0; 36 else { 37 ctmp = (ctmp - ktmp) / (1.0 - ktmp); 38 mtmp = (mtmp - ktmp) / (1.0 - ktmp); 39 ytmp = (ytmp - ktmp) / (1.0 - ktmp); 40 } 41 *c = (JSAMPLE)(255.0 - ctmp * 255.0 + 0.5); 42 *m = (JSAMPLE)(255.0 - mtmp * 255.0 + 0.5); 43 *y = (JSAMPLE)(255.0 - ytmp * 255.0 + 0.5); 44 *k = (JSAMPLE)(255.0 - ktmp * 255.0 + 0.5); 45 } 46 47 48 /* Fully reversible only for C/M/Y/K values generated with rgb_to_cmyk() */ 49 50 INLINE 51 LOCAL(void) 52 cmyk_to_rgb(JSAMPLE c, JSAMPLE m, JSAMPLE y, JSAMPLE k, JSAMPLE *r, JSAMPLE *g, 53 JSAMPLE *b) 54 { 55 *r = (JSAMPLE)((double)c * (double)k / 255.0 + 0.5); 56 *g = (JSAMPLE)((double)m * (double)k / 255.0 + 0.5); 57 *b = (JSAMPLE)((double)y * (double)k / 255.0 + 0.5); 58 } 59 60 61 #endif /* CMYK_H */ 62
