81 lines
2.1 KiB
C
81 lines
2.1 KiB
C
/* xscreensaver, Copyright (c) 1992, 1997 Jamie Zawinski <jwz@jwz.org>
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*
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* Permission to use, copy, modify, distribute, and sell this software and its
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* documentation for any purpose is hereby granted without fee, provided that
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* the above copyright notice appear in all copies and that both that
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* copyright notice and this permission notice appear in supporting
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* documentation. No representations are made about the suitability of this
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* software for any purpose. It is provided "as is" without express or
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* implied warranty.
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*/
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/* This file contains some utility routines for randomly picking the colors
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to hack the screen with.
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*/
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#include "utils.h"
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#include "hsv.h"
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void
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hsv_to_rgb (int h, double s, double v,
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unsigned short *r, unsigned short *g, unsigned short *b)
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{
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double H, S, V, R, G, B;
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double p1, p2, p3;
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double f;
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int i;
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if (s < 0) s = 0;
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if (v < 0) v = 0;
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if (s > 1) s = 1;
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if (v > 1) v = 1;
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S = s; V = v;
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H = (h % 360) / 60.0;
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i = H;
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f = H - i;
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p1 = V * (1 - S);
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p2 = V * (1 - (S * f));
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p3 = V * (1 - (S * (1 - f)));
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if (i == 0) { R = V; G = p3; B = p1; }
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else if (i == 1) { R = p2; G = V; B = p1; }
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else if (i == 2) { R = p1; G = V; B = p3; }
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else if (i == 3) { R = p1; G = p2; B = V; }
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else if (i == 4) { R = p3; G = p1; B = V; }
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else { R = V; G = p1; B = p2; }
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*r = R * 65535;
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*g = G * 65535;
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*b = B * 65535;
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}
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void
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rgb_to_hsv (unsigned short r, unsigned short g, unsigned short b,
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int *h, double *s, double *v)
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{
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double R, G, B, H, S, V;
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double cmax, cmin;
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double cmm;
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int imax;
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R = ((double) r) / 65535.0;
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G = ((double) g) / 65535.0;
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B = ((double) b) / 65535.0;
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cmax = R; cmin = G; imax = 1;
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if ( cmax < G ) { cmax = G; cmin = R; imax = 2; }
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if ( cmax < B ) { cmax = B; imax = 3; }
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if ( cmin > B ) { cmin = B; }
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cmm = cmax - cmin;
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V = cmax;
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if (cmm == 0)
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S = H = 0;
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else
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{
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S = cmm / cmax;
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if (imax == 1) H = (G - B) / cmm;
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else if (imax == 2) H = 2.0 + (B - R) / cmm;
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else /*if (imax == 3)*/ H = 4.0 + (R - G) / cmm;
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if (H < 0) H += 6.0;
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}
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*h = (H * 60.0);
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*s = S;
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*v = V;
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}
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