1 /* xscreensaver, Copyright (c) 1992 Jamie Zawinski <jwz@lucid.com>
3 * Permission to use, copy, modify, distribute, and sell this software and its
4 * documentation for any purpose is hereby granted without fee, provided that
5 * the above copyright notice appear in all copies and that both that
6 * copyright notice and this permission notice appear in supporting
7 * documentation. No representations are made about the suitability of this
8 * software for any purpose. It is provided "as is" without express or
12 /* This file contains some utility routines for randomly picking the colors
13 to hack the screen with.
19 hsv_to_rgb (h,s,v, r,g,b)
21 double s, v; /* 0.0 - 1.0 */
22 unsigned short *r, *g, *b; /* 0 - 65535 */
24 double H, S, V, R, G, B;
33 p2 = V * (1 - (S * f));
34 p3 = V * (1 - (S * (1 - f)));
35 if (i == 0) { R = V; G = p3; B = p1; }
36 else if (i == 1) { R = p2; G = V; B = p1; }
37 else if (i == 2) { R = p1; G = V; B = p3; }
38 else if (i == 3) { R = p1; G = p2; B = V; }
39 else if (i == 4) { R = p3; G = p1; B = V; }
40 else { R = V; G = p1; B = p2; }
47 rgb_to_hsv (r,g,b, h,s,v)
48 unsigned short r, g, b; /* 0 - 65535 */
50 double *s, *v; /* 0.0 - 1.0 */
52 double R, G, B, H, S, V;
56 R = ((double) r) / 65535.0;
57 G = ((double) g) / 65535.0;
58 B = ((double) b) / 65535.0;
59 cmax = R; cmin = G; imax = 1;
60 if ( cmax < G ) { cmax = G; cmin = R; imax = 2; }
61 if ( cmax < B ) { cmax = B; imax = 3; }
62 if ( cmin > B ) { cmin = B; }
70 if (imax == 1) H = (G - B) / cmm;
71 else if (imax == 2) H = 2.0 + (B - R) / cmm;
72 else if (imax == 3) H = 4.0 + (R - G) / cmm;
82 make_color_ramp (h1, s1, v1, h2, s2, v2,
84 int h1, h2; /* 0 - 360 */
85 double s1, s2, v1, v2; /* 0.0 - 1.0 */
89 int dh = (h2 - h1) / npixels;
90 double ds = (s2 - s1) / npixels;
91 double dv = (v2 - v1) / npixels;
93 for (i = 0; i < npixels; i++)
94 hsv_to_rgb ((h1 += dh), (s1 += ds), (v1 += dv),
95 &pixels [i].red, &pixels [i].green, &pixels [i].blue);
100 cycle_hue (color, degrees)
106 rgb_to_hsv (color->red, color->green, color->blue,
108 h = (h + degrees) % 360;
109 hsv_to_rgb (h, s, v, &color->red, &color->green, &color->blue);