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., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <config.h>
  23
  24 #include <stdlib.h>
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <X11/Xlib.h>
  28
  29 #include <assert.h>
  30
  31 #include "wraster.h"
  32
  33 #define MIN(a,b)        ((a)<(b) ? (a) : (b))
  34 #define MAX(a,b)        ((a)>(b) ? (a) : (b))
  35
  36 #define MIN3(a,b,c)     MIN(MIN(a,b), c)
  37 #define MAX3(a,b,c)     MAX(MAX(a,b), c)
  38
  39 void RHSVtoRGB(RHSVColor * hsv, RColor * rgb)
  40 {
  41         int h = hsv->hue % 360;
  42         int s = hsv->saturation;
  43         int v = hsv->value;
  44         int i, f;
  45         int p, q, t;
  46
  47         if (s == 0) {
  48                 rgb->red = rgb->green = rgb->blue = v;
  49                 return;
  50         }
  51         i = h / 60;
  52         f = h % 60;
  53         p = v * (255 - s) / 255;
  54         q = v * (255 - s * f / 60) / 255;
  55         t = v * (255 - s * (60 - f) / 60) / 255;
  56
  57         switch (i) {
  58         case 0:
  59                 rgb->red = v;
  60                 rgb->green = t;
  61                 rgb->blue = p;
  62                 break;
  63         case 1:
  64                 rgb->red = q;
  65                 rgb->green = v;
  66                 rgb->blue = p;
  67                 break;
  68         case 2:
  69                 rgb->red = p;
  70                 rgb->green = v;
  71                 rgb->blue = t;
  72                 break;
  73         case 3:
  74                 rgb->red = p;
  75                 rgb->green = q;
  76                 rgb->blue = v;
  77                 break;
  78         case 4:
  79                 rgb->red = t;
  80                 rgb->green = p;
  81                 rgb->blue = v;
  82                 break;
  83         case 5:
  84                 rgb->red = v;
  85                 rgb->green = p;
  86                 rgb->blue = q;
  87                 break;
  88         }
  89 }
  90
  91 void RRGBtoHSV(RColor * rgb, RHSVColor * hsv)
  92 {
  93         int h, s, v;
  94         int max = MAX3(rgb->red, rgb->green, rgb->blue);
  95         int min = MIN3(rgb->red, rgb->green, rgb->blue);
  96
  97         v = max;
  98
  99         if (max == 0)
 100                 s = 0;
 101         else
 102                 s = (max - min) * 255 / max;
 103
 104         if (s == 0)
 105                 h = 0;
 106         else {
 107                 int rc, gc, bc;
 108
 109                 rc = (max - rgb->red) * 255 / (max - min);
 110                 gc = (max - rgb->green) * 255 / (max - min);
 111                 bc = (max - rgb->blue) * 255 / (max - min);
 112
 113                 if (rgb->red == max) {
 114                         h = ((bc - gc) * 60 / 255);
 115                 } else if (rgb->green == max) {
 116                         h = 2 * 60 + ((rc - bc) * 60 / 255);
 117                 } else {
 118                         h = 4 * 60 + ((gc - rc) * 60 / 255);
 119                 }
 120                 if (h < 0)
 121                         h += 360;
 122         }
 123
 124         hsv->hue = h;
 125         hsv->saturation = s;
 126         hsv->value = v;
 127 }