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GUAC-240: Improve PNG optimality approximation algorithm (count average run length).

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This commit is contained in:
Michael Jumper 2015-08-17 11:02:18 -07:00
parent b0db2c210f
commit 2d66ae87f9
1 changed files with 6 additions and 5 deletions
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11
src/common/guac_surface.c
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@ -334,7 +334,8 @@ static int guac_common_surface_png_optimality(guac_common_surface* surface,
int x, y; int x, y;
int similarity = 0; int num_same = 0;
int num_different = 1;
/* Get image/buffer metrics */ /* Get image/buffer metrics */
int width = rect->width; int width = rect->width;
@ -356,12 +357,12 @@ static int guac_common_surface_png_optimality(guac_common_surface* surface,
/* Get next pixel */ /* Get next pixel */
uint32_t current_pixel = *(row++) | 0xFF000000; uint32_t current_pixel = *(row++) | 0xFF000000;
/* Update similarity according to whether pixel is identical */ /* Update same/different counts according to pixel value */
if (x != 0) { if (x != 0) {
if (current_pixel == last_pixel) if (current_pixel == last_pixel)
similarity++; num_same++;
else else
similarity--; num_different++;
} }
last_pixel = current_pixel; last_pixel = current_pixel;
@ -374,7 +375,7 @@ static int guac_common_surface_png_optimality(guac_common_surface* surface,
} }
/* Return rough approximation of optimality for PNG compression */ /* Return rough approximation of optimality for PNG compression */
return 0xFF * similarity / width / height; return 0x100 * num_same / num_different - 0x400;
} }