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Fix the calculation of the input image shift when using subpixel regions

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Jorge Rodriguez 2015-11-10 11:29:16 -08:00
commit c81f0c62bc
1 changed files with 8 additions and 8 deletions
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16
stb_image_resize.h
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@ -1004,31 +1004,31 @@ stbir__inline static int stbir__edge_wrap(stbir_edge edge, int n, int max)
} }
// What input pixels contribute to this output pixel? // What input pixels contribute to this output pixel?
static void stbir__calculate_sample_range_upsample(int n, float out_filter_radius, float scale_ratio, float out_shift, int* in_first_pixel, int* in_last_pixel, float* in_center_of_out) static void stbir__calculate_sample_range_upsample(int n, float out_filter_radius, float scale_ratio, float in_shift, int* in_first_pixel, int* in_last_pixel, float* in_center_of_out)
{ {
float out_pixel_center = (float)n + 0.5f; float out_pixel_center = (float)n + 0.5f;
float out_pixel_influence_lowerbound = out_pixel_center - out_filter_radius; float out_pixel_influence_lowerbound = out_pixel_center - out_filter_radius;
float out_pixel_influence_upperbound = out_pixel_center + out_filter_radius; float out_pixel_influence_upperbound = out_pixel_center + out_filter_radius;
float in_pixel_influence_lowerbound = (out_pixel_influence_lowerbound + out_shift) / scale_ratio; float in_pixel_influence_lowerbound = out_pixel_influence_lowerbound / scale_ratio + in_shift;
float in_pixel_influence_upperbound = (out_pixel_influence_upperbound + out_shift) / scale_ratio; float in_pixel_influence_upperbound = out_pixel_influence_upperbound / scale_ratio + in_shift;
*in_center_of_out = (out_pixel_center + out_shift) / scale_ratio; *in_center_of_out = out_pixel_center / scale_ratio + in_shift;
*in_first_pixel = (int)(floor(in_pixel_influence_lowerbound + 0.5)); *in_first_pixel = (int)(floor(in_pixel_influence_lowerbound + 0.5));
*in_last_pixel = (int)(floor(in_pixel_influence_upperbound - 0.5)); *in_last_pixel = (int)(floor(in_pixel_influence_upperbound - 0.5));
} }
// What output pixels does this input pixel contribute to? // What output pixels does this input pixel contribute to?
static void stbir__calculate_sample_range_downsample(int n, float in_pixels_radius, float scale_ratio, float out_shift, int* out_first_pixel, int* out_last_pixel, float* out_center_of_in) static void stbir__calculate_sample_range_downsample(int n, float in_pixels_radius, float scale_ratio, float in_shift, int* out_first_pixel, int* out_last_pixel, float* out_center_of_in)
{ {
float in_pixel_center = (float)n + 0.5f; float in_pixel_center = (float)n + 0.5f;
float in_pixel_influence_lowerbound = in_pixel_center - in_pixels_radius; float in_pixel_influence_lowerbound = in_pixel_center - in_pixels_radius;
float in_pixel_influence_upperbound = in_pixel_center + in_pixels_radius; float in_pixel_influence_upperbound = in_pixel_center + in_pixels_radius;
float out_pixel_influence_lowerbound = in_pixel_influence_lowerbound * scale_ratio - out_shift; float out_pixel_influence_lowerbound = (in_pixel_influence_lowerbound - in_shift) * scale_ratio;
float out_pixel_influence_upperbound = in_pixel_influence_upperbound * scale_ratio - out_shift; float out_pixel_influence_upperbound = (in_pixel_influence_upperbound - in_shift) * scale_ratio;
*out_center_of_in = in_pixel_center * scale_ratio - out_shift; *out_center_of_in = (in_pixel_center - in_shift) * scale_ratio;
*out_first_pixel = (int)(floor(out_pixel_influence_lowerbound + 0.5)); *out_first_pixel = (int)(floor(out_pixel_influence_lowerbound + 0.5));
*out_last_pixel = (int)(floor(out_pixel_influence_upperbound - 0.5)); *out_last_pixel = (int)(floor(out_pixel_influence_upperbound - 0.5));
} }