objects/dither.c

   1 /*
   2  * Dithering functions
   3  *
   4  * Copyright 1994 Alexandre Julliard
   5  *
   6 static char Copyright[] = "Copyright  Alexandre Julliard, 1994";
   7 */
   8
   9 #include <stdlib.h>
  10 #include <X11/Xlib.h>
  11 #include <X11/Xutil.h>
  12 #include "color.h"
  13 #include "gdi.h"
  14 #include "bitmap.h"
  15
  16
  17   /* Levels of each primary */
  18 #define PRIMARY_LEVELS  3
  19 #define TOTAL_LEVELS    (PRIMARY_LEVELS*PRIMARY_LEVELS*PRIMARY_LEVELS)
  20
  21  /* Dithering matrix size  */
  22 #define MATRIX_SIZE     8
  23 #define MATRIX_SIZE_2   (MATRIX_SIZE*MATRIX_SIZE)
  24
  25   /* Total number of possible levels for a dithered primary color */
  26 #define DITHER_LEVELS   (MATRIX_SIZE_2 * (PRIMARY_LEVELS-1) + 1)
  27
  28   /* Dithering matrix */
  29 static const int dither_matrix[MATRIX_SIZE_2] =
  30 {
  31      0, 32,  8, 40,  2, 34, 10, 42,
  32     48, 16, 56, 24, 50, 18, 58, 26,
  33     12, 44,  4, 36, 14, 46,  6, 38,
  34     60, 28, 52, 20, 62, 30, 54, 22,
  35      3, 35, 11, 43,  1, 33,  9, 41,
  36     51, 19, 59, 27, 49, 17, 57, 25,
  37     15, 47,  7, 39, 13, 45,  5, 37,
  38     63, 31, 55, 23, 61, 29, 53, 21
  39 };
  40
  41   /* Mapping between (R,G,B) triples and EGA colors */
  42 static const int EGAmapping[TOTAL_LEVELS] =
  43 {
  44     0,  /* 000000 -> 000000 */
  45     4,  /* 00007f -> 000080 */
  46     12, /* 0000ff -> 0000ff */
  47     2,  /* 007f00 -> 008000 */
  48     6,  /* 007f7f -> 008080 */
  49     6,  /* 007fff -> 008080 */
  50     10, /* 00ff00 -> 00ff00 */
  51     6,  /* 00ff7f -> 008080 */
  52     14, /* 00ffff -> 00ffff */
  53     1,  /* 7f0000 -> 800000 */
  54     5,  /* 7f007f -> 800080 */
  55     5,  /* 7f00ff -> 800080 */
  56     3,  /* 7f7f00 -> 808000 */
  57     8,  /* 7f7f7f -> 808080 */
  58     7,  /* 7f7fff -> c0c0c0 */
  59     3,  /* 7fff00 -> 808000 */
  60     7,  /* 7fff7f -> c0c0c0 */
  61     7,  /* 7fffff -> c0c0c0 */
  62     9,  /* ff0000 -> ff0000 */
  63     5,  /* ff007f -> 800080 */
  64     13, /* ff00ff -> ff00ff */
  65     3,  /* ff7f00 -> 808000 */
  66     7,  /* ff7f7f -> c0c0c0 */
  67     7,  /* ff7fff -> c0c0c0 */
  68     11, /* ffff00 -> ffff00 */
  69     7,  /* ffff7f -> c0c0c0 */
  70     15  /* ffffff -> ffffff */
  71 };
  72
  73 #define PIXEL_VALUE(r,g,b) \
  74     COLOR_mapEGAPixel[EGAmapping[((r)*PRIMARY_LEVELS+(g))*PRIMARY_LEVELS+(b)]]
  75
  76   /* X image for building dithered pixmap */
  77 static XImage *ditherImage = NULL;
  78 static char *imageData = NULL;
  79
  80
  81 /***********************************************************************
  82  *           DITHER_Init
  83  *
  84  * Create the X image used for dithering.
  85  */
  86 BOOL DITHER_Init(void)
  87 {
  88     XCREATEIMAGE( ditherImage, MATRIX_SIZE, MATRIX_SIZE, screenDepth );
  89     return (ditherImage != NULL);
  90 }
  91
  92
  93 /***********************************************************************
  94  *           DITHER_DitherColor
  95  */
  96 Pixmap DITHER_DitherColor( DC *dc, COLORREF color )
  97 {
  98     static COLORREF prevColor = 0xffffffff;
  99     unsigned int x, y;
 100     Pixmap pixmap;
 101
 102     if (color != prevColor)
 103     {
 104         int r = GetRValue( color ) * DITHER_LEVELS;
 105         int g = GetGValue( color ) * DITHER_LEVELS;
 106         int b = GetBValue( color ) * DITHER_LEVELS;
 107         const int *pmatrix = dither_matrix;
 108
 109         for (y = 0; y < MATRIX_SIZE; y++)
 110         {
 111             for (x = 0; x < MATRIX_SIZE; x++)
 112             {
 113                 int d  = *pmatrix++ * 256;
 114                 int dr = ((r + d) / MATRIX_SIZE_2) / 256;
 115                 int dg = ((g + d) / MATRIX_SIZE_2) / 256;
 116                 int db = ((b + d) / MATRIX_SIZE_2) / 256;
 117                 XPutPixel( ditherImage, x, y, PIXEL_VALUE(dr,dg,db) );
 118             }
 119         }
 120         prevColor = color;
 121     }
 122
 123     pixmap = XCreatePixmap( display, rootWindow,
 124                             MATRIX_SIZE, MATRIX_SIZE, screenDepth );
 125     XPutImage( display, pixmap, BITMAP_colorGC, ditherImage, 0, 0,
 126                0, 0, MATRIX_SIZE, MATRIX_SIZE );
 127     return pixmap;
 128 }