218 lines
6.0 KiB
C
218 lines
6.0 KiB
C
/* stb_resample - v0.1 - public domain image resampling
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no warranty implied; use at your own risk
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Do this:
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#define STB_RESAMPLE_IMPLEMENTATION
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before you include this file in *one* C or C++ file to create the implementation.
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#define STBR_ASSERT(x) to avoid using assert.h.
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Latest revisions:
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See end of file for full revision history.
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Initial implementation by Jorge L Rodriguez
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*/
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#ifndef STBR_INCLUDE_STB_RESAMPLE_H
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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, output_data, output_w, output_h, STBR_FILTER_NEAREST, STBR_EDGE_CLAMP);
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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.
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// Returned result is 1 for success or 0 in case of an error.
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typedef enum
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{
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STBR_FILTER_NEAREST = 1,
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} stbr_filter;
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typedef enum
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{
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STBR_EDGE_CLAMP = 1,
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} stbr_edge;
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typedef unsigned char stbr_uc;
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#ifdef __cplusplus
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extern "C" {
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#endif
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#ifdef STB_RESAMPLE_STATIC
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#define STBRDEF static
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#else
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#define STBRDEF extern
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#endif
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//////////////////////////////////////////////////////////////////////////////
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//
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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, stbr_uc* output_data, int output_w, int output_h, stbr_filter filter, stbr_edge edge);
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#ifdef __cplusplus
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}
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#endif
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//
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//
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//// end header file /////////////////////////////////////////////////////
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#endif // STBR_INCLUDE_STB_RESAMPLE_H
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#ifdef STB_RESIZE_IMPLEMENTATION
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#ifndef STBR_ASSERT
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#include <assert.h>
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#define STBR_ASSERT(x) assert(x)
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#endif
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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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#ifndef _MSC_VER
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#ifdef __cplusplus
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#define stbr_inline inline
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#else
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#define stbr_inline
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#endif
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#else
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#define stbr_inline __forceinline
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#endif
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#ifdef _MSC_VER
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typedef unsigned short stbr__uint16;
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typedef signed short stbr__int16;
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typedef unsigned int stbr__uint32;
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typedef signed int stbr__int32;
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#else
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#include <stdint.h>
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typedef uint16_t stbr__uint16;
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typedef int16_t stbr__int16;
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typedef uint32_t stbr__uint32;
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typedef int32_t stbr__int32;
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#endif
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// should produce compiler error if size is wrong
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typedef unsigned char stbr__validate_uint32[sizeof(stbr__uint32) == 4 ? 1 : -1];
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#ifdef _MSC_VER
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#define STBR_NOTUSED(v) (void)(v)
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#else
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#define STBR_NOTUSED(v) (void)sizeof(v)
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#endif
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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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// floating point math so we rearrange it as (n1*i0 + n1/2)/n0
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stbr_inline static int stbr__nearest_texel(int i0, int n0, int n1)
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{
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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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{
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STBR_ASSERT(x >= 0 && x < w);
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STBR_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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{
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output_data[output_texel_index] = input_data[input_texel_index];
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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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{
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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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}
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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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{
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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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}
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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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{
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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, stbr_uc* output_data, int output_w, int output_h, stbr_filter filter, stbr_edge edge)
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{
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int x, y;
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int width_stride_input = input_components * input_w;
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int width_stride_output = input_components * 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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memcpy(overwrite_contents_pre, &output_data[output_w * output_h * input_components], 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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filter_fn = &stbr__filter_nearest_n;
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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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return 0;
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#ifdef STBR_DEBUG_OVERWRITE_TEST
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STBR_ASSERT(memcmp(overwrite_contents_pre, &output_data[output_w * output_h * input_components], OVERWRITE_ARRAY_SIZE) == 0);
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#endif
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return 1;
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}
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#endif // STB_RESAMPLE_IMPLEMENTATION
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/*
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revision history:
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*/
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