objects/dither.c

/*
 * Dithering functions
 *
 * Copyright 1994 Alexandre Julliard
 */

static char Copyright[] = "Copyright  Alexandre Julliard, 1994";

#include <stdlib.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

#include "gdi.h"
#include "bitmap.h"


  /* Levels of each primary */
#define PRIMARY_LEVELS  3  
#define TOTAL_LEVELS    (PRIMARY_LEVELS*PRIMARY_LEVELS*PRIMARY_LEVELS)

 /* Dithering matrix size  */
#define MATRIX_SIZE     8
#define MATRIX_SIZE_2   (MATRIX_SIZE*MATRIX_SIZE)

  /* Total number of possible levels for a dithered primary color */
#define DITHER_LEVELS   (MATRIX_SIZE_2 * (PRIMARY_LEVELS-1) + 1)

  /* Dithering matrix */
static const int dither_matrix[MATRIX_SIZE_2] =
{
     0, 32,  8, 40,  2, 34, 10, 42,
    48, 16, 56, 24, 50, 18, 58, 26,
    12, 44,  4, 36, 14, 46,  6, 38,
    60, 28, 52, 20, 62, 30, 54, 22,
     3, 35, 11, 43,  1, 33,  9, 41,
    51, 19, 59, 27, 49, 17, 57, 25,
    15, 47,  7, 39, 13, 45,  5, 37,
    63, 31, 55, 23, 61, 29, 53, 21
};

  /* Mapping between (R,G,B) triples and EGA colors */
static const int EGAmapping[TOTAL_LEVELS] =
{
    0,  /* 000000 -> 000000 */
    4,  /* 00007f -> 000080 */
    12, /* 0000ff -> 0000ff */
    2,  /* 007f00 -> 008000 */
    6,  /* 007f7f -> 008080 */
    6,  /* 007fff -> 008080 */
    10, /* 00ff00 -> 00ff00 */
    6,  /* 00ff7f -> 008080 */
    14, /* 00ffff -> 00ffff */
    1,  /* 7f0000 -> 800000 */
    5,  /* 7f007f -> 800080 */
    5,  /* 7f00ff -> 800080 */
    3,  /* 7f7f00 -> 808000 */
    8,  /* 7f7f7f -> 808080 */
    7,  /* 7f7fff -> c0c0c0 */
    3,  /* 7fff00 -> 808000 */
    7,  /* 7fff7f -> c0c0c0 */
    7,  /* 7fffff -> c0c0c0 */
    9,  /* ff0000 -> ff0000 */
    5,  /* ff007f -> 800080 */
    13, /* ff00ff -> ff00ff */
    3,  /* ff7f00 -> 808000 */
    7,  /* ff7f7f -> c0c0c0 */
    7,  /* ff7fff -> c0c0c0 */
    11, /* ffff00 -> ffff00 */
    7,  /* ffff7f -> c0c0c0 */
    15  /* ffffff -> ffffff */
};

   /* Map an EGA index (0..15) to a pixel value */
extern int COLOR_mapEGAPixel[16];  /* in color.c */

#define PIXEL_VALUE(r,g,b) \
    COLOR_mapEGAPixel[EGAmapping[((r)*PRIMARY_LEVELS+(g))*PRIMARY_LEVELS+(b)]]

  /* X image for building dithered pixmap */
static XImage *ditherImage = NULL;
static char *imageData = NULL;


/***********************************************************************
 *           DITHER_Init
 *
 * Create the X image used for dithering.
 */
BOOL DITHER_Init()
{
    int bytes_per_line = (screenDepth * MATRIX_SIZE + 7) / 8;
    if (!(imageData = (char *) malloc( bytes_per_line * MATRIX_SIZE )))
	return FALSE;
    ditherImage = XCreateImage( display, DefaultVisualOfScreen(screen),
			        screenDepth, ZPixmap, 0, imageData,
			        MATRIX_SIZE, MATRIX_SIZE, 8, bytes_per_line );
    return (ditherImage != NULL);
}


/***********************************************************************
 *           DITHER_DitherColor
 */
Pixmap DITHER_DitherColor( DC *dc, COLORREF color )
{
    static COLORREF prevColor = 0xffffffff;
    unsigned int x, y;
    Pixmap pixmap;

/*    printf( "Dither: %x\n", color ); */

    if (color != prevColor)
    {
	int r = GetRValue( color ) * DITHER_LEVELS;
	int g = GetGValue( color ) * DITHER_LEVELS;
	int b = GetBValue( color ) * DITHER_LEVELS;
	const int *pmatrix = dither_matrix;

	WORD *mapping = (WORD *) GDI_HEAP_ADDR( dc->u.x.pal.hMapping );

	for (y = 0; y < MATRIX_SIZE; y++)
	{
	    for (x = 0; x < MATRIX_SIZE; x++)
	    {
		int d  = *pmatrix++ * 256;
		int dr = ((r + d) / MATRIX_SIZE_2) / 256;
		int dg = ((g + d) / MATRIX_SIZE_2) / 256;
		int db = ((b + d) / MATRIX_SIZE_2) / 256;
		XPutPixel( ditherImage, x, y, PIXEL_VALUE(dr,dg,db) );
	    }
	}
	prevColor = color;
    }
    
    pixmap = XCreatePixmap( display, rootWindow,
			    MATRIX_SIZE, MATRIX_SIZE, screenDepth );
    XPutImage( display, pixmap, BITMAP_colorGC, ditherImage, 0, 0,
	       0, 0, MATRIX_SIZE, MATRIX_SIZE );
    return pixmap;
}