rom/graphics/color_support.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc:
   6     Lang: english
   7 */
   8
   9 #include <exec/types.h>
  10 #include <graphics/view.h>
  11
  12 /*
  13 ** In case the representation of colors in the ColorTable of the color map
  14 ** are changed then this here should be the place where to change the
  15 ** algorithms.
  16 */
  17
  18 ULONG color_distance(struct ColorMap * cm,
  19                      ULONG r,
  20                      ULONG g,
  21                      ULONG b,
  22                      ULONG index)
  23 {
  24     /*
  25     ** I am assuming 24 bit colors that are represented in the color map as
  26     ** follows:
  27     ** cm->ColorTable is a pointer to an array of UWORDs where every
  28     **     UWORD contains the most significant 4 bits of each color.
  29     ** cm->LowColorBits is a pointer to an array of UWORDs where every
  30     **     UWORD contains the least significant 4 bits of each color.
  31     ** for example a color r=12, g=34, b=56 would be represented as:
  32     **
  33     **   cm->ColorTable[x]   = 0x0135
  34     **   cm->LowColorBits[x] = 0x0246
  35     **
  36     **   m68k graphics.library preserves high nibble of ColorTable value when changing it
  37     **   in SetRGB32cm() and SetRGB4cm() functions.
  38     **   Perhaps this has something to do with genlock support (alpha value?)
  39     **   Note that fields below ColorTable are present only if Type > COLORMAP_TYPE_V1_2
  40     */
  41
  42     WORD dr,dg,db;
  43
  44     UWORD c1 = cm->ColorTable[index];
  45     LONG r1 = (LONG)(c1 >> 4) & 0x00f0;
  46     LONG g1 = (LONG)(c1 >> 0) & 0x00f0;
  47     LONG b1 = (LONG)(c1 << 4) & 0x00f0;
  48
  49     if (cm->Type > COLORMAP_TYPE_V1_2) {
  50         UWORD c2 = cm->LowColorBits[index];
  51
  52         r1 |= (c2 >> 8) & 0x000f;
  53         g1 |= (c2 >> 4) & 0x000f;
  54         b1 |= (c2 >> 0) & 0x000f;
  55     }
  56
  57     dr = (WORD)(r >> (32-8)) - (WORD)r1;
  58     dg = (WORD)(g >> (32-8)) - (WORD)g1;
  59     db = (WORD)(b >> (32-8)) - (WORD)b1;
  60
  61     return (UWORD)(dr*dr)+(UWORD)(dg*dg)+(UWORD)(db*db);
  62 }
  63
  64
  65 /*
  66 ** Test whether the entry in the color map equals the given
  67 ** color
  68 */
  69 BOOL color_equal(struct ColorMap * cm,
  70                  ULONG r,
  71                  ULONG g,
  72                  ULONG b,
  73                  ULONG index)
  74 {
  75     if (cm->ColorTable[index] != (((r >> 20) & 0x0f00) |
  76                                               ((g >> 24) & 0x00f0) |
  77                                               ((b >> 28) & 0x000f)))
  78         return FALSE;
  79
  80     if ((cm->Type > COLORMAP_TYPE_V1_2) &&
  81        cm->LowColorBits[index] != (((r >> 16) & 0x0f00) |
  82                                                 ((g >> 20) & 0x00f0) |
  83                                                 ((b >> 24) & 0x000f)))
  84         return FALSE;
  85
  86     return TRUE;
  87 }
  88
  89 VOID color_get(struct ColorMap *cm,
  90                 ULONG *r,
  91                 ULONG *g,
  92                 ULONG *b,
  93                 ULONG index)
  94 {
  95     UWORD hibits = cm->ColorTable[index];
  96
  97     ULONG red8   = (hibits & 0x0f00) >> 4;
  98     ULONG green8 = (hibits & 0x00f0);
  99     ULONG blue8  = (hibits & 0x000f) << 4;
 100
 101     if (cm->Type > COLORMAP_TYPE_V1_2) {
 102         UWORD lobits = cm->LowColorBits[index];
 103
 104         red8   |= (lobits & 0x0f00) >> 8;
 105         green8 |= (lobits & 0x00f0) >> 4;
 106         blue8  |= (lobits & 0x000f);
 107     }
 108
 109     *r = red8   * 0x01010101;
 110     *g = green8 * 0x01010101;
 111     *b = blue8  * 0x01010101;
 112 }