在C中使用libpng读写PNG文件

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

void read_png_file(char* filename) {
    FILE* fp = fopen(filename, "rb");
    if (!fp) {
        printf("Error opening PNG file.\n");
        return;
    }

    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png_ptr) {
        printf("Error creating PNG read structure.\n");
        fclose(fp);
        return;
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        printf("Error creating PNG info structure.\n");
        png_destroy_read_struct(&png_ptr, NULL, NULL);
        fclose(fp);
        return;
    }

    png_init_io(png_ptr, fp);
    png_read_info(png_ptr, info_ptr);

    // 获取图像信息
    int width = png_get_image_width(png_ptr, info_ptr);
    int height = png_get_image_height(png_ptr, info_ptr);
    int color_type = png_get_color_type(png_ptr, info_ptr);
    int bit_depth = png_get_bit_depth(png_ptr, info_ptr);

    // 读取图像数据
    png_bytep* row_pointers = (png_bytep*)malloc(sizeof(png_bytep) * height);
    for (int y = 0; y < height; y++) {
        row_pointers[y] = (png_byte*)malloc(png_get_rowbytes(png_ptr, info_ptr));
    }
    png_read_image(png_ptr, row_pointers);

    // 处理图像数据，可以在这里进行各种图像处理操作

    // 释放内存
    for (int y = 0; y < height; y++) {
        free(row_pointers[y]);
    }
    free(row_pointers);

    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
    fclose(fp);
}

void write_png_file(char* filename, int width, int height, int color_type, int bit_depth) {
    FILE* fp = fopen(filename, "wb");
    if (!fp) {
        printf("Error opening PNG file.\n");
        return;
    }

    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png_ptr) {
        printf("Error creating PNG write structure.\n");
        fclose(fp);
        return;
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        printf("Error creating PNG info structure.\n");
        png_destroy_write_struct(&png_ptr, NULL);
        fclose(fp);
        return;
    }

    png_init_io(png_ptr, fp);

    // 设置图像信息
    png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type, PNG_INTERLACE_NONE,
                 PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

    // 写入图像数据
    png_bytep* row_pointers = (png_bytep*)malloc(sizeof(png_bytep) * height);
    for (int y = 0; y < height; y++) {
        row_pointers[y] = (png_byte*)malloc(png_get_rowbytes(png_ptr, info_ptr));
    }
    png_write_image(png_ptr, row_pointers);

    // 释放内存
    for (int y = 0; y < height; y++) {
        free(row_pointers[y]);
    }
    free(row_pointers);

    png_write_end(png_ptr, info_ptr);
    png_destroy_write_struct(&png_ptr, &info_ptr);
    fclose(fp);
}

int main() {
    char* filename = "image.png";

    // 读取PNG文件
    read_png_file(filename);

    // 写入PNG文件
    int width = 640;
    int height = 480;
    int color_type = PNG_COLOR_TYPE_RGB;
    int bit_depth = 8;
    write_png_file(filename, width, height, color_type, bit_depth);

    return 0;
}