rom/graphics/findcolor.c

   1 /*
   2     Copyright © 1995-2007, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Find the closest matching color in a colormap
   6     Lang: english
   7 */
   8 #include "graphics_intern.h"
   9 #include <graphics/view.h>
  10
  11 /*****************************************************************************
  12
  13     NAME */
  14         #include <clib/graphics_protos.h>
  15
  16         AROS_LH5(ULONG, FindColor,
  17
  18 /*  SYNOPSIS */
  19         AROS_LHA(struct ColorMap *, cm    , A3),
  20         AROS_LHA(ULONG            , r     , D1),
  21         AROS_LHA(ULONG            , g     , D2),
  22         AROS_LHA(ULONG            , b     , D3),
  23         AROS_LHA(ULONG            , maxpen, D4),
  24
  25 /*  LOCATION */
  26         struct GfxBase *, GfxBase, 168, Graphics)
  27
  28 /*  FUNCTION
  29         Find the closest matching color in the given colormap.
  30
  31     INPUTS
  32         cm - colormap structure
  33         r  - red level   (32 bit left justified fraction)
  34         g  - green level (32 bit left justified fraction)
  35         b  - blue level  (32 bit left justified fraction)
  36         maxpen - the maximum entry in the color table to search.
  37
  38     RESULT
  39         The pen number with the closest match will be returned.
  40         No new pens are allocated and therefore the returned pen
  41         should not be released via ReleasePen().
  42
  43     NOTES
  44
  45     EXAMPLE
  46
  47     BUGS
  48
  49     SEE ALSO
  50
  51     INTERNALS
  52
  53     HISTORY
  54
  55 *****************************************************************************/
  56 {
  57     AROS_LIBFUNC_INIT
  58
  59     ULONG retval = 0;
  60
  61     if (NULL != cm)
  62     {
  63         ULONG index = 0;
  64         ULONG best_distance = (ULONG)-1;
  65         ULONG distance;
  66
  67         if (-1 == maxpen && NULL != cm->PalExtra)
  68         {
  69             /* pe_SharableColors is not the number of colors but the last color index! */
  70             maxpen = cm->PalExtra->pe_SharableColors;
  71         }
  72
  73         if (maxpen >= cm->Count) maxpen = cm->Count - 1;
  74
  75         while (index <= maxpen)
  76         {
  77             distance = color_distance(cm,r,g,b,index);
  78             if (distance < best_distance)
  79             {
  80                 best_distance = distance;
  81                 retval = index;
  82             }
  83             index++;
  84         }
  85     }
  86
  87     return retval;
  88
  89     AROS_LIBFUNC_EXIT
  90 } /* FindColor */