src/shared/color-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <math.h>
   4
   5 #include "color-util.h"
   6 #include "macro.h"
   7
   8 void rgb_to_hsv(double r, double g, double b,
   9                 double *ret_h, double *ret_s, double *ret_v) {
  10
  11         assert(r >= 0 && r <= 1);
  12         assert(g >= 0 && g <= 1);
  13         assert(b >= 0 && b <= 1);
  14         assert(ret_h);
  15         assert(ret_s);
  16         assert(ret_v);
  17
  18         double max_color = fmax(r, fmax(g, b));
  19         double min_color = fmin(r, fmin(g, b));
  20         double delta = max_color - min_color;
  21
  22         *ret_v = max_color * 100.0;
  23
  24         if (max_color > 0)
  25                 *ret_s = delta / max_color * 100.0;
  26         else {
  27                 *ret_s = 0;
  28                 *ret_h = NAN;
  29                 return;
  30         }
  31
  32         if (delta > 0) {
  33                 if (r >= max_color)
  34                         *ret_h = 60 * fmod((g - b) / delta, 6);
  35                 else if (g >= max_color)
  36                         *ret_h = 60 * (((b - r) / delta) + 2);
  37                 else if (b >= max_color)
  38                         *ret_h = 60 * (((r - g) / delta) + 4);
  39
  40                 *ret_h = fmod(*ret_h, 360);
  41         } else
  42                 *ret_h = NAN;
  43 }
  44
  45 void hsv_to_rgb(double h, double s, double v,
  46                 uint8_t* ret_r, uint8_t *ret_g, uint8_t *ret_b) {
  47
  48         double c, x, m, r, g, b;
  49
  50         assert(s >= 0 && s <= 100);
  51         assert(v >= 0 && v <= 100);
  52         assert(ret_r);
  53         assert(ret_g);
  54         assert(ret_b);
  55
  56         h = fmod(h, 360);
  57         c = (s / 100.0) * (v / 100.0);
  58         x = c * (1 - fabs(fmod(h / 60.0, 2) - 1));
  59         m = (v / 100) - c;
  60
  61         if (h >= 0 && h < 60)
  62                 r = c, g = x, b = 0.0;
  63         else if (h >= 60 && h < 120)
  64                 r = x, g = c, b = 0.0;
  65         else if (h >= 120 && h < 180)
  66                 r = 0.0, g = c, b = x;
  67         else if (h >= 180 && h < 240)
  68                 r = 0.0, g = x, b = c;
  69         else if (h >= 240 && h < 300)
  70                 r = x, g = 0.0, b = c;
  71         else
  72                 r = c, g = 0.0, b = x;
  73
  74         *ret_r = (uint8_t) ((r + m) * 255);
  75         *ret_g = (uint8_t) ((g + m) * 255);
  76         *ret_b = (uint8_t) ((b + m) * 255);
  77 }