C++实现BGR格式转换PNG

由于PNG是一种无损压缩格式，它不支持BGR格式，因此需要将BGR转换为RGB格式后再保存为PNG格式。下面是一个简单的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <png.h>

void bgr_to_rgb(unsigned char *image, int width, int height) {
    int i, j;
    unsigned char temp;
    for (i = 0; i < height; i++) {
        for (j = 0; j < width * 3; j += 3) {
            temp = image[i * width * 3 + j];
            image[i * width * 3 + j] = image[i * width * 3 + j + 2];
            image[i * width * 3 + j + 2] = temp;
        }
    }
}

int save_png(const char *filename, unsigned char *image, int width, int height) {
    FILE *fp;
    png_structp png_ptr;
    png_infop info_ptr;
    png_byte **row_pointers;
    int i;

    fp = fopen(filename, "wb");
    if (!fp) {
        printf("Error: failed to open file %s\n", filename);
        return -1;
    }

    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png_ptr) {
        printf("Error: failed to create png write struct\n");
        fclose(fp);
        return -1;
    }

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        printf("Error: failed to create png info struct\n");
        png_destroy_write_struct(&png_ptr, NULL);
        fclose(fp);
        return -1;
    }

    if (setjmp(png_jmpbuf(png_ptr))) {
        printf("Error: failed to set png jump buffer\n");
        png_destroy_write_struct(&png_ptr, &info_ptr);
        fclose(fp);
        return -1;
    }

    png_init_io(png_ptr, fp);
    png_set_IHDR(png_ptr, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB,
                 PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
    png_write_info(png_ptr, info_ptr);

    row_pointers = (png_byte **)png_malloc(png_ptr, height * sizeof(png_byte *));
    for (i = 0; i < height; i++) {
        row_pointers[i] = image + i * width * 3;
    }

    png_write_image(png_ptr, row_pointers);
    png_write_end(png_ptr, NULL);
    png_free(png_ptr, row_pointers);
    png_destroy_write_struct(&png_ptr, &info_ptr);
    fclose(fp);

    return 0;
}

int main(int argc, char **argv) {
    int width = 640;
    int height = 480;
    unsigned char *image = (unsigned char *)malloc(width * height * 3);

    // 填充BGR格式数据
    // ...

    // 转换为RGB格式
    bgr_to_rgb(image, width, height);

    // 保存为PNG格式
    save_png("output.png", image, width, height);

    free(image);
    return 0;
}

需要注意的是，以上代码只是一个简单的示例，实际应用中可能会有更多的错误检查和处理。