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fast realization with moving window.

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linear speed against any radius
This commit is contained in:
homm 2014-10-12 17:47:00 +04:00
parent a6937d84d8
commit cc9eff5c68
1 changed files with 47 additions and 18 deletions
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65
libImaging/BoxBlur.c
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@ -7,36 +7,65 @@ HorizontalBoxBlur32(Imaging im, Imaging imOut, int radius)
{
ImagingSectionCookie cookie;
int x, y, pix, offset;
int x, y, pix;
int acc[4];
typedef UINT8 pixel[4];
pixel *line;
int lastx = im->xsize - 1;
int window = radius * 2 + 1;
#define SAVE(acc) \
(UINT8)(acc[0] / window) | (UINT8)(acc[1] / window) << 8 | \
(UINT8)(acc[2] / window) << 16 | (UINT8)(acc[3] / window) << 24
#define MOVE_ACC(acc, substract, add) \
acc[0] -= line[substract][0]; \
acc[1] -= line[substract][1]; \
acc[2] -= line[substract][2]; \
acc[3] -= line[substract][3]; \
acc[0] += line[add][0]; \
acc[1] += line[add][1]; \
acc[2] += line[add][2]; \
acc[3] += line[add][3];
ImagingSectionEnter(&cookie);
for (y = 0; y < im->ysize; y++) {
line = (pixel *) im->image32[y];
for (x = 0; x < im->xsize; x++) {
acc[0] = acc[1] = acc[2] = acc[3] = 0;
for (pix = x - radius; pix <= x + radius; pix++) {
offset = pix;
if (pix < 0) {
offset = 0;
} else if (pix >= im->xsize) {
offset = im->xsize - 1;
}
acc[0] += line[offset][0];
acc[1] += line[offset][1];
acc[2] += line[offset][2];
acc[3] += line[offset][3];
}
imOut->image32[y][x] =
(UINT8)(acc[0] / window) | (UINT8)(acc[1] / window) << 8 |
(UINT8)(acc[2] / window) << 16 | (UINT8)(acc[3] / window) << 24;
/* Compute acc for -1 pixel (outside of image):
From "-radius-1" to "0" get first pixel,
then from "1" to "radius-1". */
acc[0] = line[0][0] * (radius + 2);
acc[1] = line[0][1] * (radius + 2);
acc[2] = line[0][2] * (radius + 2);
acc[3] = line[0][3] * (radius + 2);
for (pix = 1; pix < radius; pix++) {
acc[0] += line[pix][0];
acc[1] += line[pix][1];
acc[2] += line[pix][2];
acc[3] += line[pix][3];
}
/* Substract pixel from left ("0").
Add pixels from radius. */
for (x = 0; x <= radius; x++) {
MOVE_ACC(acc, 0, x + radius);
imOut->image32[y][x] = SAVE(acc);
}
/* Substract previous pixel from "-radius".
Add pixels from radius. */
for (x = radius + 1; x < im->xsize - radius; x++) {
MOVE_ACC(acc, x - radius - 1, x + radius);
imOut->image32[y][x] = SAVE(acc);
}
/* Substract previous pixel from "-radius".
Add last pixel. */
for (x = im->xsize - radius; x < im->xsize; x++) {
MOVE_ACC(acc, x - radius - 1, lastx);
imOut->image32[y][x] = SAVE(acc);
}
}