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 #include "wr_i18n.h"
  34
  35
  36 #define MIN(a,b)        ((a)<(b) ? (a) : (b))
  37 #define MAX(a,b)        ((a)>(b) ? (a) : (b))
  38
  39 #define MIN3(a,b,c)     MIN(MIN(a,b), c)
  40 #define MAX3(a,b,c)     MAX(MAX(a,b), c)
  41
  42 void RHSVtoRGB(const RHSVColor * hsv, RColor * rgb)
  43 {
  44         int h = hsv->hue % 360;
  45         int s = hsv->saturation;
  46         int v = hsv->value;
  47         int i, f;
  48         int p, q, t;
  49
  50         if (s == 0) {
  51                 rgb->red = rgb->green = rgb->blue = v;
  52                 return;
  53         }
  54         i = h / 60;
  55         f = h % 60;
  56         p = v * (255 - s) / 255;
  57         q = v * (255 - s * f / 60) / 255;
  58         t = v * (255 - s * (60 - f) / 60) / 255;
  59
  60         switch (i) {
  61         case 0:
  62                 rgb->red = v;
  63                 rgb->green = t;
  64                 rgb->blue = p;
  65                 break;
  66         case 1:
  67                 rgb->red = q;
  68                 rgb->green = v;
  69                 rgb->blue = p;
  70                 break;
  71         case 2:
  72                 rgb->red = p;
  73                 rgb->green = v;
  74                 rgb->blue = t;
  75                 break;
  76         case 3:
  77                 rgb->red = p;
  78                 rgb->green = q;
  79                 rgb->blue = v;
  80                 break;
  81         case 4:
  82                 rgb->red = t;
  83                 rgb->green = p;
  84                 rgb->blue = v;
  85                 break;
  86         case 5:
  87                 rgb->red = v;
  88                 rgb->green = p;
  89                 rgb->blue = q;
  90                 break;
  91         }
  92 }
  93
  94 void RRGBtoHSV(const RColor * rgb, RHSVColor * hsv)
  95 {
  96         int h, s, v;
  97         int max = MAX3(rgb->red, rgb->green, rgb->blue);
  98         int min = MIN3(rgb->red, rgb->green, rgb->blue);
  99
 100         v = max;
 101
 102         if (max == 0)
 103                 s = 0;
 104         else
 105                 s = (max - min) * 255 / max;
 106
 107         if (s == 0)
 108                 h = 0;
 109         else {
 110                 int rc, gc, bc;
 111
 112                 rc = (max - rgb->red) * 255 / (max - min);
 113                 gc = (max - rgb->green) * 255 / (max - min);
 114                 bc = (max - rgb->blue) * 255 / (max - min);
 115
 116                 if (rgb->red == max) {
 117                         h = ((bc - gc) * 60 / 255);
 118                 } else if (rgb->green == max) {
 119                         h = 2 * 60 + ((rc - bc) * 60 / 255);
 120                 } else {
 121                         h = 4 * 60 + ((gc - rc) * 60 / 255);
 122                 }
 123                 if (h < 0)
 124                         h += 360;
 125         }
 126
 127         hsv->hue = h;
 128         hsv->saturation = s;
 129         hsv->value = v;
 130 }