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
21
22 /* Fully reversible */
23
24 INLINE
LOCAL(void)25 LOCAL(void)
26 rgb_to_cmyk(JSAMPLE r, JSAMPLE g, JSAMPLE b, JSAMPLE *c, JSAMPLE *m,
27 JSAMPLE *y, JSAMPLE *k)
28 {
29 double ctmp = 1.0 - ((double)r / 255.0);
30 double mtmp = 1.0 - ((double)g / 255.0);
31 double ytmp = 1.0 - ((double)b / 255.0);
32 double ktmp = MIN(MIN(ctmp, mtmp), ytmp);
33
34 if (ktmp == 1.0) ctmp = mtmp = ytmp = 0.0;
35 else {
36 ctmp = (ctmp - ktmp) / (1.0 - ktmp);
37 mtmp = (mtmp - ktmp) / (1.0 - ktmp);
38 ytmp = (ytmp - ktmp) / (1.0 - ktmp);
39 }
40 *c = (JSAMPLE)(255.0 - ctmp * 255.0 + 0.5);
41 *m = (JSAMPLE)(255.0 - mtmp * 255.0 + 0.5);
42 *y = (JSAMPLE)(255.0 - ytmp * 255.0 + 0.5);
43 *k = (JSAMPLE)(255.0 - ktmp * 255.0 + 0.5);
44 }
45
46
47 /* Fully reversible only for C/M/Y/K values generated with rgb_to_cmyk() */
48
49 INLINE
LOCAL(void)50 LOCAL(void)
51 cmyk_to_rgb(JSAMPLE c, JSAMPLE m, JSAMPLE y, JSAMPLE k, JSAMPLE *r, JSAMPLE *g,
52 JSAMPLE *b)
53 {
54 *r = (JSAMPLE)((double)c * (double)k / 255.0 + 0.5);
55 *g = (JSAMPLE)((double)m * (double)k / 255.0 + 0.5);
56 *b = (JSAMPLE)((double)y * (double)k / 255.0 + 0.5);
57 }
58
59
60 #endif /* CMYK_H */
61