apps/plugins/lib/rgb_hsv.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2006 Antoine Cellerier <dionoea -at- videolan -dot- org>
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21
  22 #include "rgb_hsv.h"
  23
  24 /***********************************************************************
  25  * Colorspace transformations
  26  ***********************************************************************
  27  * r, g and b range from 0 to 255
  28  * h ranges from 0 to 3599 (which in fact means 0.0 to 359.9).
  29  *   360 is the same as 0 (it loops)
  30  * s and v range from 0 to 255 (which in fact means 0.00 to 1.00)
  31  ***********************************************************************/
  32
  33 void rgb2hsv( int r, int g, int b, int *h, int *s, int *v )
  34 {
  35     int max;
  36     int min;
  37
  38     max = r > g ? r : g;
  39     if( b > max ) max = b;
  40
  41     min = r < g ? r : g;
  42     if( b < min ) min = b;
  43
  44     if( max == 0 )
  45     {
  46         *v = 0;
  47         *h = 0; *s = 0; /* Random since it's black */
  48         return;
  49     }
  50     else if( max == min )
  51     {
  52         *h = 0; /* Random since it's gray */
  53     }
  54     else if( max == r && g >= b )
  55     {
  56         *h = ( 10 * 60 * ( g - b )/( max - min ) );
  57     }
  58     else if( max == r && g < b )
  59     {
  60         *h = ( 10 * ( 60 * ( g - b )/( max - min ) + 360 ));
  61     }
  62     else if( max == g )
  63     {
  64         *h = ( 10 * ( 60 * ( b - r )/( max - min ) + 120 ));
  65     }
  66     else// if( max == b )
  67     {
  68         *h = ( 10 * ( 60 * ( r - g )/( max - min ) + 240 ));
  69     }
  70
  71     /* Just in case ? */
  72     while( *h < 0 ) *h += 3600;
  73     while( *h >= 3600 ) *h-= 3600;
  74
  75     *s = (( max - min )*255)/max;
  76     *v = max;
  77 }
  78
  79 void hsv2rgb( int h, int s, int v, int *r, int *g, int *b )
  80 {
  81     int f, p, q, t;
  82     while( h < 0 ) h += 3600;
  83     while( h >= 3600 ) h-= 3600;
  84     f = h%600;
  85     p = ( v * ( 255 - s ) ) / ( 255 );
  86     q = ( v * ( 600*255 - f*s ) ) / ( 255 * 600 );
  87     t = ( v * ( 600*255 - ( 600 - f ) * s ) ) / ( 255 * 600 );
  88
  89
  90     if( s == 0 ) /* gray */
  91     {
  92         *r = v;
  93         *g = *r;
  94         *b = *r;
  95         return;
  96     }
  97
  98     switch( h/600 )
  99     {
 100         case 0:
 101             *r = v;
 102             *g = t;
 103             *b = p;
 104             break;
 105         case 1:
 106             *r = q;
 107             *g = v;
 108             *b = p;
 109             break;
 110         case 2:
 111             *r = p;
 112             *g = v;
 113             *b = t;
 114             break;
 115         case 3:
 116             *r = p;
 117             *g = q;
 118             *b = v;
 119             break;
 120         case 4:
 121             *r = t;
 122             *g = p;
 123             *b = v;
 124             break;
 125         case 5:
 126             *r = v;
 127             *g = p;
 128             *b = q;
 129             break;
 130     }
 131 }