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  * All files in this archive are subject to the GNU General Public License.
  13  * See the file COPYING in the source tree root for full license agreement.
  14  *
  15  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  16  * KIND, either express or implied.
  17  *
  18  ****************************************************************************/
  19
  20 #include "rgb_hsv.h"
  21
  22 /***********************************************************************
  23  * Colorspace transformations
  24  ***********************************************************************
  25  * r, g and b range from 0 to 255
  26  * h ranges from 0 to 3599 (which in fact means 0.0 to 359.9).
  27  *   360 is the same as 0 (it loops)
  28  * s and v range from 0 to 255 (which in fact means 0.00 to 1.00)
  29  ***********************************************************************/
  30
  31 void rgb2hsv( int r, int g, int b, int *h, int *s, int *v )
  32 {
  33     int max;
  34     int min;
  35
  36     max = r > g ? r : g;
  37     if( b > max ) max = b;
  38
  39     min = r < g ? r : g;
  40     if( b < min ) min = b;
  41
  42     if( max == 0 )
  43     {
  44         *v = 0;
  45         *h = 0; *s = 0; /* Random since it's black */
  46         return;
  47     }
  48     else if( max == min )
  49     {
  50         *h = 0; /* Random since it's gray */
  51     }
  52     else if( max == r && g >= b )
  53     {
  54         *h = ( 10 * 60 * ( g - b )/( max - min ) );
  55     }
  56     else if( max == r && g < b )
  57     {
  58         *h = ( 10 * ( 60 * ( g - b )/( max - min ) + 360 ));
  59     }
  60     else if( max == g )
  61     {
  62         *h = ( 10 * ( 60 * ( b - r )/( max - min ) + 120 ));
  63     }
  64     else// if( max == b )
  65     {
  66         *h = ( 10 * ( 60 * ( r - g )/( max - min ) + 240 ));
  67     }
  68
  69     /* Just in case ? */
  70     while( *h < 0 ) *h += 3600;
  71     while( *h >= 3600 ) *h-= 3600;
  72
  73     *s = (( max - min )*255)/max;
  74     *v = max;
  75 }
  76
  77 void hsv2rgb( int h, int s, int v, int *r, int *g, int *b )
  78 {
  79     int f, p, q, t;
  80     while( h < 0 ) h += 3600;
  81     while( h >= 3600 ) h-= 3600;
  82     f = h%600;
  83     p = ( v * ( 255 - s ) ) / ( 255 );
  84     q = ( v * ( 600*255 - f*s ) ) / ( 255 * 600 );
  85     t = ( v * ( 600*255 - ( 600 - f ) * s ) ) / ( 255 * 600 );
  86
  87
  88     if( s == 0 ) /* gray */
  89     {
  90         *r = v;
  91         *g = *r;
  92         *b = *r;
  93         return;
  94     }
  95
  96     switch( h/600 )
  97     {
  98         case 0:
  99             *r = v;
 100             *g = t;
 101             *b = p;
 102             break;
 103         case 1:
 104             *r = q;
 105             *g = v;
 106             *b = p;
 107             break;
 108         case 2:
 109             *r = p;
 110             *g = v;
 111             *b = t;
 112             break;
 113         case 3:
 114             *r = p;
 115             *g = q;
 116             *b = v;
 117             break;
 118         case 4:
 119             *r = t;
 120             *g = p;
 121             *b = v;
 122             break;
 123         case 5:
 124             *r = v;
 125             *g = p;
 126             *b = q;
 127             break;
 128     }
 129 }