试试这种抖动算法。
https://en.wikipedia.org/wiki/Ordered_dithering
============================================
/* Dither Tresshold for Red Channel */
static const BYTE dither_tresshold_r[64] = {
1, 7, 3, 5, 0, 8, 2, 6,
7, 1, 5, 3, 8, 0, 6, 2,
3, 5, 0, 8, 2, 6, 1, 7,
5, 3, 8, 0, 6, 2, 7, 1,
0, 8, 2, 6, 1, 7, 3, 5,
8, 0, 6, 2, 7, 1, 5, 3,
2, 6, 1, 7, 3, 5, 0, 8,
6, 2, 7, 1, 5, 3, 8, 0
};
/* Dither Tresshold for Green Channel */
static const BYTE dither_tresshold_g[64] = {
1, 3, 2, 2, 3, 1, 2, 2,
2, 2, 0, 4, 2, 2, 4, 0,
3, 1, 2, 2, 1, 3, 2, 2,
2, 2, 4, 0, 2, 2, 0, 4,
1, 3, 2, 2, 3, 1, 2, 2,
2, 2, 0, 4, 2, 2, 4, 0,
3, 1, 2, 2, 1, 3, 2, 2,
2, 2, 4, 0, 2, 2, 0, 4
};
/* Dither Tresshold for Blue Channel */
static const BYTE dither_tresshold_b[64] = {
5, 3, 8, 0, 6, 2, 7, 1,
3, 5, 0, 8, 2, 6, 1, 7,
8, 0, 6, 2, 7, 1, 5, 3,
0, 8, 2, 6, 1, 7, 3, 5,
6, 2, 7, 1, 5, 3, 8, 0,
2, 6, 1, 7, 3, 5, 0, 8,
7, 1, 5, 3, 8, 0, 6, 2,
1, 7, 3, 5, 0, 8, 2, 6
};
/* Get 16bit closest color */
BYTE closest_rb(BYTE c) {
return (c >> 3 << 3); /* red & blue */
}
BYTE closest_g(BYTE c) {
return (c >> 2 << 2); /* green */
}
/* RGB565 */
WORD RGB16BIT(BYTE r, BYTE g, BYTE b) {
return ((WORD)((r>>3)<<11)|((g>>2)<<5)|(b>>3));
}
/* Dithering by individual subpixel */
WORD dither_xy(
int x,
int y,
BYTE r,
BYTE g,
BYTE b
){
/* Get Tresshold Index */
BYTE tresshold_id = ((y & 7) << 3) + (x & 7);
r = closest_rb(
MIN(r + dither_tresshold_r[tresshold_id], 0xff)
);
g = closest_g(
MIN(g + dither_tresshold_g[tresshold_id], 0xff)
);
b = closest_rb(
MIN(b + dither_tresshold_b[tresshold_id], 0xff)
);
return RGB16BIT(r, g, b);
}
/* Dithering Pixel from 32/24bit RGB
*
* GetR, GetG, GetB -> Function to get individual color in pixel
*
*/
WORD dither_color_xy(int x, int y, DWORD col) {
return dither_xy(x, y, GetR(col), GetG(col), GetB(col));
}
/* EXAMPLES */
void ExampleDither1(WORD * dest, DWORD * src, int width, int height){
int x, y;
for (y=0; y<height; y++){
for (x=0; x<width; x++){
int pos = y * width + x;
dest[pos] = dither_color_xy(x,y,src[pos]);
}
}
}
void ExampleDither2(WORD * dest, BYTE * src, int width, int height){
int x, y;
for (y=0; y<height; y++){
for (x=0; x<width; x++){
int pos = y * width + x;
dest[pos] = dither_xy(x,y,src[pos*3],src[pos*3+1],src[pos*3+2]);
}
}
} |