wrlib/color.c

   1 /* color.c - color stuff (rgb -> hsv convertion etc.)
   2  *
   3  * Raster graphics library
   4  *
   5  * Copyright (c) 1998-2003 Alfredo K. Kojima
   6  *
   7  *  This library is free software; you can redistribute it and/or
   8  *  modify it under the terms of the GNU Library General Public
   9  *  License as published by the Free Software Foundation; either
  10  *  version 2 of the License, or (at your option) any later version.
  11  *
  12  *  This library is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  *  Library General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU Library General Public
  18  *  License along with this library; if not, write to the Free
  19  *  Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
  20  *  MA 02110-1301, USA.
  21  */
  22
  23 #include <config.h>
  24
  25 #include <stdlib.h>
  26 #include <stdio.h>
  27 #include <string.h>
  28 #include <X11/Xlib.h>
  29
  30 #include <assert.h>
  31
  32 #include "wraster.h"
  33
  34 #define MIN(a,b)        ((a)<(b) ? (a) : (b))
  35 #define MAX(a,b)        ((a)>(b) ? (a) : (b))
  36
  37 #define MIN3(a,b,c)     MIN(MIN(a,b), c)
  38 #define MAX3(a,b,c)     MAX(MAX(a,b), c)
  39
  40 void RHSVtoRGB(const RHSVColor * hsv, RColor * rgb)
  41 {
  42         int h = hsv->hue % 360;
  43         int s = hsv->saturation;
  44         int v = hsv->value;
  45         int i, f;
  46         int p, q, t;
  47
  48         if (s == 0) {
  49                 rgb->red = rgb->green = rgb->blue = v;
  50                 return;
  51         }
  52         i = h / 60;
  53         f = h % 60;
  54         p = v * (255 - s) / 255;
  55         q = v * (255 - s * f / 60) / 255;
  56         t = v * (255 - s * (60 - f) / 60) / 255;
  57
  58         switch (i) {
  59         case 0:
  60                 rgb->red = v;
  61                 rgb->green = t;
  62                 rgb->blue = p;
  63                 break;
  64         case 1:
  65                 rgb->red = q;
  66                 rgb->green = v;
  67                 rgb->blue = p;
  68                 break;
  69         case 2:
  70                 rgb->red = p;
  71                 rgb->green = v;
  72                 rgb->blue = t;
  73                 break;
  74         case 3:
  75                 rgb->red = p;
  76                 rgb->green = q;
  77                 rgb->blue = v;
  78                 break;
  79         case 4:
  80                 rgb->red = t;
  81                 rgb->green = p;
  82                 rgb->blue = v;
  83                 break;
  84         case 5:
  85                 rgb->red = v;
  86                 rgb->green = p;
  87                 rgb->blue = q;
  88                 break;
  89         }
  90 }
  91
  92 void RRGBtoHSV(const RColor * rgb, RHSVColor * hsv)
  93 {
  94         int h, s, v;
  95         int max = MAX3(rgb->red, rgb->green, rgb->blue);
  96         int min = MIN3(rgb->red, rgb->green, rgb->blue);
  97
  98         v = max;
  99
 100         if (max == 0)
 101                 s = 0;
 102         else
 103                 s = (max - min) * 255 / max;
 104
 105         if (s == 0)
 106                 h = 0;
 107         else {
 108                 int rc, gc, bc;
 109
 110                 rc = (max - rgb->red) * 255 / (max - min);
 111                 gc = (max - rgb->green) * 255 / (max - min);
 112                 bc = (max - rgb->blue) * 255 / (max - min);
 113
 114                 if (rgb->red == max) {
 115                         h = ((bc - gc) * 60 / 255);
 116                 } else if (rgb->green == max) {
 117                         h = 2 * 60 + ((rc - bc) * 60 / 255);
 118                 } else {
 119                         h = 4 * 60 + ((gc - rc) * 60 / 255);
 120                 }
 121                 if (h < 0)
 122                         h += 360;
 123         }
 124
 125         hsv->hue = h;
 126         hsv->saturation = s;
 127         hsv->value = v;
 128 }