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Add mitchell filter.

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This commit is contained in:
Jorge Rodriguez 2014-07-26 15:06:31 -07:00
parent 69af963c42
commit fb2f8df5cc
1 changed files with 16 additions and 0 deletions
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16
stb_resample.h
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@ -31,6 +31,7 @@ typedef enum
STBR_FILTER_BILINEAR = 2, STBR_FILTER_BILINEAR = 2,
STBR_FILTER_BICUBIC = 3, // A cubic b spline STBR_FILTER_BICUBIC = 3, // A cubic b spline
STBR_FILTER_CATMULLROM = 4, STBR_FILTER_CATMULLROM = 4,
STBR_FILTER_MITCHELL = 5,
} stbr_filter; } stbr_filter;
typedef enum typedef enum
@ -260,12 +261,27 @@ static float stbr__filter_catmullrom(float x)
return (0.0f); return (0.0f);
} }
static float stbr__filter_mitchell(float x)
{
x = (float)fabs(x);
float xx = x*x;
if (x < 1.0f)
return 1.1666666666666f * (x * xx) - 2 * xx + 0.8888888888f;
else if (x < 2.0f)
return -0.3888888888f * (x * xx) + 2 * xx - 3.333333333f * x + 1.777777777777f;
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_bilinear, 1.0f }, { stbr__filter_bilinear, 1.0f },
{ stbr__filter_bicubic, 2.0f }, { stbr__filter_bicubic, 2.0f },
{ stbr__filter_catmullrom, 2.0f }, { stbr__filter_catmullrom, 2.0f },
{ stbr__filter_mitchell, 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)