1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193
|
/*
* ordered dither rotines
*
* stolen from The GIMP and trimmed for speed
*
*/
#include <stdlib.h>
#include "dither.h"
#define DITHER_LEVEL 8
void (*dither_line)(unsigned char *, unsigned char *, int, int);
static long red_mult, green_mult;
static long red_dither[256];
static long green_dither[256];
static long blue_dither[256];
static long gray_dither[256];
typedef unsigned long vector[DITHER_LEVEL];
typedef vector matrix[DITHER_LEVEL];
#if DITHER_LEVEL == 8
#define DITHER_MASK 7
static matrix DM =
{
{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}
};
#endif
#if DITHER_LEVEL == 4
#define DITHER_MASK 3
static matrix DM =
{
{0, 8, 2, 10},
{12, 4, 14, 6},
{3, 11, 1, 9},
{15, 7, 13, 5}
};
#endif
void
init_dither(int shades_r, int shades_g, int shades_b, int shades_gray)
{
int i, j;
unsigned char low_shade, high_shade;
unsigned short index;
float red_colors_per_shade;
float green_colors_per_shade;
float blue_colors_per_shade;
float gray_colors_per_shade;
red_mult = shades_g * shades_b;
green_mult = shades_b;
red_colors_per_shade = 256.0 / (shades_r - 1);
green_colors_per_shade = 256.0 / (shades_g - 1);
blue_colors_per_shade = 256.0 / (shades_b - 1);
gray_colors_per_shade = 256.0 / (shades_gray - 1);
/* this avoids a shift when checking these values */
for (i = 0; i < DITHER_LEVEL; i++)
for (j = 0; j < DITHER_LEVEL; j++)
DM[i][j] *= 0x10000;
/* setup arrays containing three bytes of information for red, green, & blue */
/* the arrays contain :
* 1st byte: low end shade value
* 2nd byte: high end shade value
* 3rd & 4th bytes: ordered dither matrix index
*/
for (i = 0; i < 256; i++) {
/* setup the red information */
{
low_shade = (unsigned char) (i / red_colors_per_shade);
high_shade = low_shade + 1;
index = (unsigned short)
(((i - low_shade * red_colors_per_shade) / red_colors_per_shade) *
(DITHER_LEVEL * DITHER_LEVEL + 1));
low_shade *= red_mult;
high_shade *= red_mult;
red_dither[i] = (index << 16) + (high_shade << 8) + (low_shade);
}
/* setup the green information */
{
low_shade = (unsigned char) (i / green_colors_per_shade);
high_shade = low_shade + 1;
index = (unsigned short)
(((i - low_shade * green_colors_per_shade) / green_colors_per_shade) *
(DITHER_LEVEL * DITHER_LEVEL + 1));
low_shade *= green_mult;
high_shade *= green_mult;
green_dither[i] = (index << 16) + (high_shade << 8) + (low_shade);
}
/* setup the blue information */
{
low_shade = (unsigned char) (i / blue_colors_per_shade);
high_shade = low_shade + 1;
index = (unsigned short)
(((i - low_shade * blue_colors_per_shade) / blue_colors_per_shade) *
(DITHER_LEVEL * DITHER_LEVEL + 1));
blue_dither[i] = (index << 16) + (high_shade << 8) + (low_shade);
}
/* setup the gray information */
{
low_shade = (unsigned char) (i / gray_colors_per_shade);
high_shade = low_shade + 1;
index = (unsigned short)
(((i - low_shade * gray_colors_per_shade) / gray_colors_per_shade) *
(DITHER_LEVEL * DITHER_LEVEL + 1));
gray_dither[i] = (index << 16) + (high_shade << 8) + (low_shade);
}
}
}
void
dither_line_color(unsigned char *src, unsigned char *dest, int y, int width)
{
register long a, b;
long *ymod, xmod;
ymod = DM[y & DITHER_MASK];
while (width--) {
xmod = width & DITHER_MASK;
b = red_dither[*(src++)];
if (ymod[xmod] < b)
b >>= 8;
a = green_dither[*(src++)];
if (ymod[xmod] < a)
a >>= 8;
b += a;
a = blue_dither[*(src++)];
if (ymod[xmod] < a)
a >>= 8;
b += a;
*(dest++) = b & 0xff;
}
}
void
dither_line_gray(unsigned char *src, unsigned char *dest, int y, int width)
{
long *ymod, xmod;
register long a,g;
ymod = DM[y & DITHER_MASK];
while (width--) {
xmod = width & DITHER_MASK;
#if 1
g = (src[0]*3 + src[1]*6 + src[2]) / 10;
a = gray_dither[g];
src += 3;
#else
a = gray_dither[*(src++)];
#endif
if (ymod[xmod] < a)
a >>= 8;
*(dest++) = a & 0xff;
}
}
|