src/apps/icon-o-matic/generic/support/rgb_hsv.h

   1 /*
   2  * Copyright 2001 Werner Freytag - please read to the LICENSE file
   3  *
   4  */
   5 #ifndef CONVERT_RGB_HSV_H
   6 #define CONVERT_RGB_HSV_H
   7
   8
   9 #include <math.h>
  10
  11
  12 #define RETURN_HSV(h, s, v) { H = h; S = s; V = v; return; }
  13 #define RETURN_RGB(r, g, b) { R = r; G = g; B = b; return; }
  14
  15 #define UNDEFINED 0
  16
  17
  18 inline void
  19 RGB_to_HSV(float R, float G, float B, float& H, float& S, float& V)
  20 {
  21         // RGB are each on [0, 1]. S and max are returned on [0, 1] and H is
  22         // returned on [0, 6]. Exception: H is returned UNDEFINED if S==0.
  23
  24         float min, max;
  25
  26         if (R > G) {
  27                 if (R > B) {
  28                         max = R;
  29                         min = G > B ? B : G;
  30                 } else {
  31                         max = B;
  32                         min = G;
  33                 }
  34         }
  35         else {
  36                 if (G > B) {
  37                         max = G;
  38                         min = R > B ? B : R;
  39                 } else {
  40                         max = B;
  41                         min = R;
  42                 }
  43         }
  44
  45         if (max == min)
  46                 RETURN_HSV(UNDEFINED, 0, max);
  47
  48         float dist = max - min;
  49
  50         float f = (R == min)
  51                 ? G - B
  52                 : ((G == min) ? B - R : R - G);
  53         float i = (R == min)
  54                 ? 3
  55                 : ((G == min) ? 5 : 1);
  56         float h = i - f / dist;
  57
  58         while (h >= 6.0)
  59                 h -= 6.0;
  60
  61         RETURN_HSV(h, dist/max, max);
  62 }
  63
  64
  65 inline void
  66 HSV_to_RGB(float h, float s, float v, float& R, float& G, float& B)
  67 {
  68         // H is given on [0, 6] or UNDEFINED. S and V are given on [0, 1].
  69         // RGB are each returned on [0, 1].
  70
  71         int i = (int)floor(h);
  72
  73         float f = h - i;
  74
  75         if ( !(i & 1) )
  76                 f = 1 - f; // if i is even
  77
  78         float m = v * (1 - s);
  79
  80         float n = v * (1 - s * f);
  81
  82         switch (i) {
  83                 case 6:
  84                 case 0:
  85                         RETURN_RGB(v, n, m);
  86
  87                 case 1:
  88                         RETURN_RGB(n, v, m);
  89
  90                 case 2:
  91                         RETURN_RGB(m, v, n)
  92
  93                 case 3:
  94                         RETURN_RGB(m, n, v);
  95
  96                 case 4:
  97                         RETURN_RGB(n, m, v);
  98
  99                 case 5:
 100                         RETURN_RGB(v, m, n);
 101
 102                 default:
 103                         RETURN_RGB(0, 0, 0);
 104         }
 105 }
 106
 107
 108 #endif // CONVERT_RGB_HSV_H