简单易用的图像解码库介绍 —— stb_image

 1#include <iostream>
 2
 3#define STB_IMAGE_IMPLEMENTATION
 4#include "stb_image.h"
 5#define STB_IMAGE_WRITE_IMPLEMENTATION
 6#include "stb_image_write.h"
 7#define STB_IMAGE_RESIZE_IMPLEMENTATION
 8#include "stb_image_resize.h"
 9#include <string>
10#include <stdio.h>
11#include <stdlib.h>
12#include <vector>
13
14using namespace std;
15
16int main() {
17    std::cout << "Hello, STB_Image" << std::endl;
18
19    string inputPath = "/Users/glumes/Pictures/input.png";
20    int iw, ih, n;
21
22    // 加载图片获取宽、高、颜色通道信息
23    unsigned char *idata = stbi_load(inputPath.c_str(), &iw, &ih, &n, 0);
24
25    int ow = iw / 2;
26    int oh = ih / 2;
27    auto *odata = (unsigned char *) malloc(ow * oh * n);
28
29    // 改变图片尺寸
30    stbir_resize(idata, iw, ih, 0, odata, ow, oh, 0, STBIR_TYPE_UINT8, n, STBIR_ALPHA_CHANNEL_NONE, 0,
31                 STBIR_EDGE_CLAMP, STBIR_EDGE_CLAMP,
32                 STBIR_FILTER_BOX, STBIR_FILTER_BOX,
33                 STBIR_COLORSPACE_SRGB, nullptr
34    );
35
36    string outputPath = "/Users/glumes/Pictures/output.png";
37    // 写入图片
38    stbi_write_png(outputPath.c_str(), ow, oh, n, odata, 0);
39
40    stbi_image_free(idata);
41    stbi_image_free(odata);
42    return 0;
43}

1STBIRDEF int stbir_resize(const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
2                             void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
3                             stbir_datatype datatype,
4                             int num_channels, int alpha_channel, int flags,
5                             // stb 中提供了多种模式，但是修改后并没有见很明显的效果
6                             stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical, 
7                             stbir_filter filter_horizontal,  stbir_filter filter_vertical,
8                             stbir_colorspace space, void *alloc_context)
9

 1typedef enum
 2{
 3    STBIR_EDGE_CLAMP   = 1,
 4    STBIR_EDGE_REFLECT = 2,
 5    STBIR_EDGE_WRAP    = 3,
 6    STBIR_EDGE_ZERO    = 4,
 7} stbir_edge;
 8
 9typedef enum
10{
11    STBIR_FILTER_DEFAULT      = 0,  // use same filter type that easy-to-use API chooses
12    STBIR_FILTER_BOX          = 1,  // A trapezoid w/1-pixel wide ramps, same result as box for integer scale ratios
13    STBIR_FILTER_TRIANGLE     = 2,  // On upsampling, produces same results as bilinear texture filtering
14    STBIR_FILTER_CUBICBSPLINE = 3,  // The cubic b-spline (aka Mitchell-Netrevalli with B=1,C=0), gaussian-esque
15    STBIR_FILTER_CATMULLROM   = 4,  // An interpolating cubic spline
16    STBIR_FILTER_MITCHELL     = 5,  // Mitchell-Netrevalli filter with B=1/3, C=1/3
17} stbir_filter;

1int stbi_write_jpg(char const *filename, int x, int y, int comp, const void *data, int quality)
2
3int stbi_write_png(char const *filename, int x, int y, int comp, const void *data, int stride_bytes)
4