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Skip zero-coefficient contributors, a fairly decent speedup.

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This commit is contained in:
Jorge Rodriguez 2014-09-10 20:26:14 -07:00
parent 46dc8f84fb
commit 793818d1af
1 changed files with 18 additions and 0 deletions
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18
stb_image_resize.h
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@ -843,6 +843,15 @@ static void stbir__calculate_coefficients_upsample(stbir__info* stbir_info, stbi
for (i = 0; i <= in_last_pixel - in_first_pixel; i++) for (i = 0; i <= in_last_pixel - in_first_pixel; i++)
coefficient_group[i] *= filter_scale; coefficient_group[i] *= filter_scale;
for (i = in_last_pixel - in_first_pixel; i >= 0; i--)
{
if (coefficient_group[i])
break;
// This line has no weight. We can skip it.
contributor->n1 = contributor->n0 + i - 1;
}
} }
static void stbir__calculate_coefficients_downsample(stbir__info* stbir_info, stbir_filter filter, float scale_ratio, int out_first_pixel, int out_last_pixel, float out_center_of_in, stbir__contributors* contributor, float* coefficient_group) static void stbir__calculate_coefficients_downsample(stbir__info* stbir_info, stbir_filter filter, float scale_ratio, int out_first_pixel, int out_last_pixel, float out_center_of_in, stbir__contributors* contributor, float* coefficient_group)
@ -862,6 +871,15 @@ static void stbir__calculate_coefficients_downsample(stbir__info* stbir_info, st
float x = out_pixel_center - out_center_of_in; float x = out_pixel_center - out_center_of_in;
coefficient_group[i] = stbir__filter_info_table[filter].kernel(x, scale_ratio) * scale_ratio; coefficient_group[i] = stbir__filter_info_table[filter].kernel(x, scale_ratio) * scale_ratio;
} }
for (i = out_last_pixel - out_first_pixel; i >= 0; i--)
{
if (coefficient_group[i])
break;
// This line has no weight. We can skip it.
contributor->n1 = contributor->n0 + i - 1;
}
} }
static void stbir__normalize_downsample_coefficients(stbir__info* stbir_info) static void stbir__normalize_downsample_coefficients(stbir__info* stbir_info)