mirror of
https://github.com/nothings/stb
synced 2025-01-06 14:52:00 +03:00
Beginning of a more sophisticated resample algorithm, starting with calculating filter contributions per scan line.
This commit is contained in:
Jorge Rodriguez
parent
0155bd3ab6
commit
55c5f0b3a0
249
stb_resample.h
249
stb_resample.h
@ -18,7 +18,7 @@ Initial implementation by Jorge L Rodriguez
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#define STBR_INCLUDE_STB_RESAMPLE_H
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// Basic usage:
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// result = stbr_resize(input_data, input_w, input_h, input_components, 0, output_data, output_w, output_h, 0, STBR_FILTER_NEAREST, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB);
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// result = stbr_resize(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, channels, alpha_channel, STBR_TYPE_UINT8, STBR_FILTER_BILINEAR, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB);
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//
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// input_data is your supplied texels.
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// output_data will be the resized texels. It should be of size output_w * output_h * input_components (or output_h * output_stride if you provided a stride.)
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@ -38,11 +38,16 @@ typedef enum
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typedef enum
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{
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STBR_COLORSPACE_LINEAR = 1,
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STBR_COLORSPACE_SRGB = 1,
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STBR_COLORSPACE_SRGB = 2,
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} stbr_colorspace;
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typedef enum
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{
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STBR_TYPE_UINT8 = 1,
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} stbr_type;
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typedef unsigned char stbr_uc;
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typedef unsigned int stbr_size_t; // to avoid including a header for size_t
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#ifdef __cplusplus
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extern "C" {
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@ -59,7 +64,15 @@ extern "C" {
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// PRIMARY API - resize an image
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//
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STBRDEF int stbr_resize(const stbr_uc* input_data, int input_w, int input_h, int input_components, int input_stride, stbr_uc* output_data, int output_w, int output_h, int output_stride, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace);
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STBRDEF stbr_size_t stbr_calculate_memory(int input_w, int input_h, int input_stride_in_bytes,
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int output_w, int output_h, int output_stride_in_bytes,
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int channels, stbr_filter filter);
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STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input_h, int input_stride_in_bytes,
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void* output_data, int output_w, int output_h, int output_stride_in_bytes,
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//int channels, int alpha_channel, stbr_type type, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace,
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int channels, stbr_type type, stbr_filter filter,
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void* tempmem, stbr_size_t tempmem_size_in_bytes);
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#ifdef __cplusplus
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@ -78,13 +91,21 @@ extern "C" {
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#define STBR_ASSERT(x) assert(x)
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#endif
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#ifdef STBR_DEBUG
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#define STBR_DEBUG_ASSERT STBR_ASSERT
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#else
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#define STBR_DEBUG_ASSERT
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#endif
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// If you hit this it means I haven't done it yet.
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#define STBR_UNIMPLEMENTED(x) STBR_ASSERT(!(x))
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#ifdef STBR_DEBUG_OVERWRITE_TEST
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#include <string.h>
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#endif
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// For size_t
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#include <stdlib.h>
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#include <math.h>
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#ifndef _MSC_VER
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@ -120,6 +141,64 @@ typedef unsigned char stbr__validate_uint32[sizeof(stbr__uint32) == 4 ? 1 : -1];
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#define STBR_NOTUSED(v) (void)sizeof(v)
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#endif
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#define STBR_ARRAY_SIZE(a) (sizeof((a))/sizeof((a)[0]))
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// Kernel function centered at 0
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typedef float (stbr__kernel_fn)(float x);
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typedef struct
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{
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stbr__kernel_fn* kernel;
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float support;
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} stbr__filter_info;
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typedef struct
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{
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int n0; // First contributing source texel
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int n1; // Last contributing source texel
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} stbr__contributors;
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typedef struct
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{
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int total_contributors;
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int kernel_texel_width;
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float* decode_buffer;
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stbr__contributors* horizontal_contributors;
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float* horizontal_coefficients;
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} stbr__info;
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float stbr__filter_nearest(float x)
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{
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if (fabs(x) < 0.5)
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return 1;
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else
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return 0;
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}
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stbr__filter_info stbr__filter_info_table[] = {
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{ NULL, 0.0f },
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{ stbr__filter_nearest, 0.5f },
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};
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// This is the maximum number of input samples that can affect an output sample
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// with the given filter
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int stbr__get_filter_texel_width(stbr_filter filter, int upsample)
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{
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STBR_UNIMPLEMENTED(!upsample);
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STBR_ASSERT(filter != 0);
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STBR_ASSERT(filter < STBR_ARRAY_SIZE(stbr__filter_info_table));
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return (int)ceil(stbr__filter_info_table[filter].support * 2);
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}
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int stbr__get_total_contributors(stbr_filter filter, int input_w, int output_w)
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{
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return output_w * stbr__get_filter_texel_width(filter, output_w > input_w ? 1 : 0);
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}
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// i0 is a texel in [0, n0-1]
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// What's the nearest texel center to i0's center in [0, n1-1] ?
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// Remapping [0, n0-1] to [0, n1-1] gives (i0 + 0.5)*n1/n0 but we want to avoid
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@ -129,95 +208,143 @@ stbr_inline static int stbr__nearest_texel(int i0, int n0, int n1)
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return (n1*i0 + n1/2) / n0;
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}
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stbr_inline static size_t stbr__texel_index(int x, int y, int c, int width_stride, int num_c, int w, int h)
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stbr_inline static stbr_size_t stbr__texel_index(int x, int y, int c, int width_stride, int num_c, int w, int h)
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{
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STBR_ASSERT(x >= 0 && x < w);
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STBR_ASSERT(y >= 0 && y < h);
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STBR_DEBUG_ASSERT(x >= 0 && x < w);
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STBR_DEBUG_ASSERT(y >= 0 && y < h);
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return y*width_stride + x*num_c + c;
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}
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static void stbr__filter_nearest_1(const stbr_uc* input_data, stbr_uc* output_data, size_t input_texel_index, size_t output_texel_index, size_t n)
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stbr_inline static stbr__contributors* stbr__get_contributor(stbr__info* stbr_info, int n)
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{
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output_data[output_texel_index] = input_data[input_texel_index];
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return &stbr_info->horizontal_contributors[n];
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}
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static void stbr__filter_nearest_3(const stbr_uc* input_data, stbr_uc* output_data, size_t input_texel_index, size_t output_texel_index, size_t n)
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stbr_inline static float* stbr__get_coefficient(stbr__info* stbr_info, int n, int c)
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{
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output_data[output_texel_index] = input_data[input_texel_index];
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output_data[output_texel_index + 1] = input_data[input_texel_index + 1];
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output_data[output_texel_index + 2] = input_data[input_texel_index + 2];
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return &stbr_info->horizontal_coefficients[stbr_info->kernel_texel_width*n + c];
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}
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static void stbr__filter_nearest_4(const stbr_uc* input_data, stbr_uc* output_data, size_t input_texel_index, size_t output_texel_index, size_t n)
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// Each scan line uses the same kernel values so we should calculate the kernel
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// values once and then we can use them for every scan line.
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static void stbr__calculate_horizontal_filters(stbr__info* stbr_info, stbr_filter filter, int input_w, int output_w)
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{
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output_data[output_texel_index] = input_data[input_texel_index];
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output_data[output_texel_index + 1] = input_data[input_texel_index + 1];
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output_data[output_texel_index + 2] = input_data[input_texel_index + 2];
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output_data[output_texel_index + 3] = input_data[input_texel_index + 3];
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int n, i;
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float scale_ratio = (float)output_w / input_w;
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float out_pixels_radius = stbr__filter_info_table[filter].support * scale_ratio;
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STBR_UNIMPLEMENTED(output_w < input_w);
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for (n = 0; n < output_w; n++)
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{
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// What input texels contribute to this output texel?
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float out_texel_center = (float)n + 0.5f;
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float out_texel_influence_lowerbound = out_texel_center - out_pixels_radius;
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float out_texel_influence_upperbound = out_texel_center + out_pixels_radius;
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float in_center_of_out = out_texel_center / scale_ratio;
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float in_texel_influence_lowerbound = out_texel_influence_lowerbound / scale_ratio;
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float in_texel_influence_upperbound = out_texel_influence_upperbound / scale_ratio;
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int in_first_texel = (int)(floor(in_texel_influence_lowerbound + 0.5));
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int in_last_texel = (int)(floor(in_texel_influence_upperbound - 0.5));
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float total_filter = 0;
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float filter_scale;
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STBR_DEBUG_ASSERT(in_last_texel - in_first_texel <= stbr_info->kernel_texel_width);
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STBR_DEBUG_ASSERT(in_first_texel >= 0);
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STBR_DEBUG_ASSERT(in_last_texel < input_w);
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stbr__get_contributor(stbr_info, n)->n0 = in_first_texel;
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stbr__get_contributor(stbr_info, n)->n1 = in_last_texel;
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for (i = 0; i <= in_last_texel - in_first_texel; i++)
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{
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float in_texel_center = (float)(i + in_first_texel) + 0.5f;
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total_filter += *stbr__get_coefficient(stbr_info, n, i) = stbr__filter_info_table[filter].kernel(in_center_of_out - in_texel_center);
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}
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STBR_DEBUG_ASSERT(total_filter > 0);
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STBR_DEBUG_ASSERT(fabs(1-total_filter) < 0.1f); // Make sure it's not way off.
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// Make sure the sum of all coefficients is 1.
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filter_scale = 1 / total_filter;
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for (i = 0; i <= in_last_texel - in_first_texel; i++)
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*stbr__get_coefficient(stbr_info, n, i) *= filter_scale;
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}
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}
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static void stbr__filter_nearest_n(const stbr_uc* input_data, stbr_uc* output_data, size_t input_texel_index, size_t output_texel_index, size_t n)
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STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input_h, int input_stride_in_bytes,
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void* output_data, int output_w, int output_h, int output_stride_in_bytes,
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int channels, stbr_type type, stbr_filter filter,
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void* tempmem, stbr_size_t tempmem_size_in_bytes)
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{
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size_t c;
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for (c = 0; c < n; c++)
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output_data[output_texel_index + c] = input_data[input_texel_index + c];
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}
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typedef void (stbr__filter_fn)(const stbr_uc* input_data, stbr_uc* output_data, size_t input_texel_index, size_t output_texel_index, size_t n);
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STBRDEF int stbr_resize(const stbr_uc* input_data, int input_w, int input_h, int input_components, int input_stride, stbr_uc* output_data, int output_w, int output_h, int output_stride, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace)
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{
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int x, y;
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int width_stride_input = input_stride ? input_stride : input_components * input_w;
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int width_stride_output = output_stride ? output_stride : input_components * output_w;
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int width_stride_input = input_stride_in_bytes ? input_stride_in_bytes : channels * input_w;
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int width_stride_output = output_stride_in_bytes ? output_stride_in_bytes : channels * output_w;
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#ifdef STBR_DEBUG_OVERWRITE_TEST
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#define OVERWRITE_ARRAY_SIZE 64
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unsigned char overwrite_contents_pre[OVERWRITE_ARRAY_SIZE];
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size_t begin_forbidden = width_stride_output * (output_h - 1) + output_w * input_components;
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memcpy(overwrite_contents_pre, &output_data[begin_forbidden], OVERWRITE_ARRAY_SIZE);
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stbr_size_t begin_forbidden = width_stride_output * (output_h - 1) + output_w * channels;
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memcpy(overwrite_contents_pre, &((unsigned char*)output_data)[begin_forbidden], OVERWRITE_ARRAY_SIZE);
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#endif
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if (filter == STBR_FILTER_NEAREST)
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{
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stbr__filter_fn* filter_fn;
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STBR_UNIMPLEMENTED(type != STBR_TYPE_UINT8);
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filter_fn = &stbr__filter_nearest_n;
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STBR_ASSERT(filter != 0);
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STBR_ASSERT(filter < STBR_ARRAY_SIZE(stbr__filter_info_table));
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if (input_components == 1)
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filter_fn = &stbr__filter_nearest_1;
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else if (input_components == 3)
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filter_fn = &stbr__filter_nearest_3;
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else if (input_components == 4)
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filter_fn = &stbr__filter_nearest_4;
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for (y = 0; y < output_h; y++)
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{
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int nearest_y = stbr__nearest_texel(y, output_h, input_h);
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for (x = 0; x < output_w; x++)
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{
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int nearest_x = stbr__nearest_texel(x, output_w, input_w);
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size_t input_texel_index = stbr__texel_index(nearest_x, nearest_y, 0, width_stride_input, input_components, input_w, input_h);
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size_t output_texel_index = stbr__texel_index(x, y, 0, width_stride_output, input_components, output_w, output_h);
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filter_fn(input_data, output_data, input_texel_index, output_texel_index, input_components);
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}
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}
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}
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else
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if (!tempmem)
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return 0;
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if (tempmem_size_in_bytes < stbr_calculate_memory(input_w, input_h, input_stride_in_bytes, output_w, output_h, output_stride_in_bytes, channels, STBR_FILTER_NEAREST))
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return 0;
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#define STBR__NEXT_MEMPTR(current, old, newtype) (newtype*)(((unsigned char*)current) + old)
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memset(tempmem, 0, tempmem_size_in_bytes);
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stbr__info* stbr_info = (stbr__info*)tempmem;
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stbr_info->total_contributors = stbr__get_total_contributors(filter, input_w, output_w);
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stbr_info->kernel_texel_width = stbr__get_filter_texel_width(filter, output_w > input_w ? 1 : 0);
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stbr_info->decode_buffer = STBR__NEXT_MEMPTR(stbr_info, sizeof(stbr__info), float);
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stbr_info->horizontal_contributors = STBR__NEXT_MEMPTR(stbr_info->decode_buffer, input_w * channels * sizeof(float), stbr__contributors);
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stbr_info->horizontal_coefficients = STBR__NEXT_MEMPTR(stbr_info->horizontal_contributors, stbr_info->total_contributors * sizeof(stbr__contributors), float);
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#undef STBR__NEXT_MEMPTR
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stbr__calculate_horizontal_filters(stbr_info, filter, input_w, output_w);
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#ifdef STBR_DEBUG_OVERWRITE_TEST
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STBR_ASSERT(memcmp(overwrite_contents_pre, &output_data[begin_forbidden], OVERWRITE_ARRAY_SIZE) == 0);
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STBR_DEBUG_ASSERT(memcmp(overwrite_contents_pre, &((unsigned char*)output_data)[begin_forbidden], OVERWRITE_ARRAY_SIZE) == 0);
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#endif
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return 1;
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}
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STBRDEF stbr_size_t stbr_calculate_memory(int input_w, int input_h, int input_stride_in_bytes,
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int output_w, int output_h, int output_stride_in_bytes,
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int channels, stbr_filter filter)
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{
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STBR_ASSERT(filter != 0);
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STBR_ASSERT(filter < STBR_ARRAY_SIZE(stbr__filter_info_table));
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int info_size = sizeof(stbr__info);
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int decode_buffer_size = input_w * channels * sizeof(float);
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int contributors_size = stbr__get_total_contributors(filter, input_w, output_w) * sizeof(stbr__contributors);
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int coefficients_size = stbr__get_total_contributors(filter, input_w, output_w) * sizeof(float);
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return info_size + decode_buffer_size + contributors_size + coefficients_size;
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}
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#endif // STB_RESAMPLE_IMPLEMENTATION
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/*
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@ -5,6 +5,7 @@
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#endif
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#define STB_RESAMPLE_IMPLEMENTATION
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#define STB_RESAMPLE_STATIC
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#include "stb_resample.h"
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#define STB_IMAGE_WRITE_IMPLEMENTATION
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@ -13,6 +14,10 @@
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#define STB_IMAGE_IMPLEMENTATION
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#include "stb_image.h"
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#ifdef _WIN32
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#include <sys/timeb.h>
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#endif
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int main(int argc, char** argv)
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{
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unsigned char* input_data;
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@ -34,14 +39,26 @@ int main(int argc, char** argv)
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return 1;
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}
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out_w = 512;
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out_h = 512;
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out_w = 1024;
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out_h = 1024;
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out_stride = (out_w + 10) * n;
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output_data = malloc(out_stride * out_h);
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output_data = (unsigned char*)malloc(out_stride * out_h);
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int in_w = 512;
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int in_h = 512;
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size_t memory_required = stbr_calculate_memory(in_w, in_h, w*n, out_w, out_h, out_stride, n, STBR_FILTER_NEAREST);
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void* extra_memory = malloc(memory_required);
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// Cut out the outside 64 pixels all around to test the stride.
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stbr_resize(input_data + w*64*n + 64*n, w - 128, h - 128, n, w*n, output_data, out_w, out_h, out_stride, STBR_FILTER_NEAREST, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB);
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int border = 64;
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STBR_ASSERT(in_w + border <= w);
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STBR_ASSERT(in_h + border <= h);
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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_NEAREST, extra_memory, memory_required);
|
||||
|
||||
free(extra_memory);
|
||||
|
||||
stbi_write_png("output.png", out_w, out_h, n, output_data, out_stride);
|
||||
|
||||
11
tests/resample_test_c.c
Normal file
11
tests/resample_test_c.c
Normal file
@ -0,0 +1,11 @@
|
||||
#ifdef _WIN32
|
||||
#define STBR_ASSERT(x) \
|
||||
if (!(x)) \
|
||||
__debugbreak();
|
||||
#endif
|
||||
|
||||
#define STB_RESAMPLE_IMPLEMENTATION
|
||||
#define STB_RESAMPLE_STATIC
|
||||
#include "stb_resample.h"
|
||||
|
||||
// Just to make sure it will build properly with a c compiler
|
||||
Loading…
Reference in New Issue
Block a user