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Add a bicubic filter.

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This commit is contained in:
Jorge Rodriguez 2014-07-26 13:07:04 -07:00
parent a95da9ee1d
commit 01fb58d6b4
2 changed files with 27 additions and 9 deletions
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26
stb_resample.h
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@ -28,7 +28,8 @@ Initial implementation by Jorge L Rodriguez
typedef enum typedef enum
{ {
STBR_FILTER_NEAREST = 1, STBR_FILTER_NEAREST = 1,
STBR_FILTER_LINEAR = 2, STBR_FILTER_BILINEAR = 2,
STBR_FILTER_BICUBIC = 3, // A cubic b spline
} stbr_filter; } stbr_filter;
typedef enum typedef enum
@ -212,13 +213,15 @@ static stbr_inline int stbr__max(int a, int b)
static float stbr__filter_nearest(float x) static float stbr__filter_nearest(float x)
{ {
if (fabs(x) <= 0.5) x = (float)fabs(x);
if (x <= 0.5)
return 1; return 1;
else else
return 0; return 0;
} }
static float stbr__filter_linear(float x) static float stbr__filter_bilinear(float x)
{ {
x = (float)fabs(x); x = (float)fabs(x);
@ -228,10 +231,25 @@ static float stbr__filter_linear(float x)
return 0; return 0;
} }
static float stbr__filter_bicubic(float x)
{
x = (float)fabs(x);
float xx = x*x;
if (x < 1.0f)
return 0.5f * (x * xx) - xx + 0.66666666666f;
else if (x < 2.0f)
return -0.16666666f * (x * xx) + xx - 2 * x + 1.3333333333f;
return (0.0f);
}
static stbr__filter_info stbr__filter_info_table[] = { static stbr__filter_info stbr__filter_info_table[] = {
{ NULL, 0.0f }, { NULL, 0.0f },
{ stbr__filter_nearest, 0.5f }, { stbr__filter_nearest, 0.5f },
{ stbr__filter_linear, 1.0f }, { stbr__filter_bilinear, 1.0f },
{ stbr__filter_bicubic, 2.0f },
}; };
stbr_inline static int stbr__use_width_upsampling_noinfo(int output_w, int input_w) stbr_inline static int stbr__use_width_upsampling_noinfo(int output_w, int input_w)

4
tests/resample_test.cpp
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@ -48,7 +48,7 @@ int main(int argc, char** argv)
int in_w = 512; int in_w = 512;
int in_h = 512; int in_h = 512;
size_t memory_required = stbr_calculate_memory(in_w, in_h, w*n, out_w, out_h, out_stride, n, STBR_FILTER_LINEAR); size_t memory_required = stbr_calculate_memory(in_w, in_h, w*n, out_w, out_h, out_stride, n, STBR_FILTER_BICUBIC);
void* extra_memory = malloc(memory_required); void* extra_memory = malloc(memory_required);
// Cut out the outside 64 pixels all around to test the stride. // Cut out the outside 64 pixels all around to test the stride.
@ -56,7 +56,7 @@ int main(int argc, char** argv)
STBR_ASSERT(in_w + border <= w); STBR_ASSERT(in_w + border <= w);
STBR_ASSERT(in_h + border <= h); STBR_ASSERT(in_h + border <= h);
stbr_resize_arbitrary(input_data + w * border * n + border * n, in_w, in_h, w*n, output_data, out_w, out_h, out_stride, n, STBR_TYPE_UINT8, STBR_FILTER_LINEAR, STBR_EDGE_CLAMP, extra_memory, memory_required); stbr_resize_arbitrary(input_data + w * border * n + border * n, in_w, in_h, w*n, output_data, out_w, out_h, out_stride, n, STBR_TYPE_UINT8, STBR_FILTER_BICUBIC, STBR_EDGE_CLAMP, extra_memory, memory_required);
free(extra_memory); free(extra_memory);