基于ARM 实现简单的电子相册功能

#include "mytype.h" // 将jpeg文件的压缩图像数据读出，放到jpg_buffer中去等待解压 unsigned long read_image_from_file(int fd, unsigned char *jpg_buffer, unsigned long jpg_size) { unsigned long nread = 0; unsigned long total = 0; while(jpg_size > 0) { nread = read(fd, jpg_buffer, jpg_size); jpg_size -= nread; jpg_buffer += nread; total += nread; } close(fd); return total; } int Stat(const char *filename, struct stat *file_info) { int ret = stat(filename, file_info); if(ret == -1) { fprintf(stderr, "[%d]: stat failed: " "%s\n", __LINE__, strerror(errno)); exit(1); } return ret; } int Open(const char *filename, int mode) { int fd = open(filename, mode); if(fd == -1) { fprintf(stderr, "[%d]: open failed: " "%s\n", __LINE__, strerror(errno)); exit(1); } return fd; } int decode_jpg(char* filename) { node_t *picture = (node_t*)malloc(sizeof(node_t)); // 读取图片文件属性信息 // 并根据其大小分配内存缓冲区jpg_buffer struct stat file_info; Stat(filename, &file_info); int fd = Open(filename, O_RDONLY); unsigned char *jpg_buffer; jpg_buffer = (unsigned char *)calloc(1, file_info.st_size); read_image_from_file(fd, jpg_buffer, file_info.st_size); /*********** 以下代码都是固定的套路 ****************/ // 声明解压缩结构体，以及错误管理结构体 struct jpeg_decompress_struct cinfo; struct jpeg_error_mgr jerr; // 使用缺省的出错处理来初始化解压缩结构体 cinfo.err = jpeg_std_error(&jerr); jpeg_create_decompress(&cinfo); // 配置该cinfo，使其从jpg_buffer中读取jpg_size个字节 // 这些数据必须是完整的JPEG数据 jpeg_mem_src(&cinfo, jpg_buffer, file_info.st_size); // 读取JPEG文件的头，并判断其格式是否合法 int ret = jpeg_read_header(&cinfo, true); if(ret != 1) { fprintf(stderr, "[%d]: jpeg_read_header failed: " "%s\n", __LINE__, strerror(errno)); exit(1); } // 开始解码 jpeg_start_decompress(&cinfo); // 妥善保管图片的尺寸信息 picture->image_info.width = cinfo.output_width; picture->image_info.height = cinfo.output_height; picture->image_info.pixel_size = cinfo.output_components; // 计算一行的字节数 int row_stride = picture->image_info.width * picture->image_info.pixel_size; // 根据图片的尺寸大小，分配一块相应的内存rgb_buffer // 用来存放从jpg_buffer解压出来的图像数据 unsigned long rgb_size; rgb_size = picture->image_info.width * picture->image_info.height * picture->image_info.pixel_size; picture->rgb_buf = (unsigned char *)calloc(1, rgb_size); // 循环地将图片的每一行读出并解码到rgb_buffer中 int line = 0; while(cinfo.output_scanline < cinfo.output_height) { unsigned char *buffer_array[1]; buffer_array[0] = picture->rgb_buf + (cinfo.output_scanline) * row_stride; jpeg_read_scanlines(&cinfo, buffer_array, 1); } // 解压完了，将jpeg相关的资源释放掉 jpeg_finish_decompress(&cinfo); jpeg_destroy_decompress(&cinfo); free(jpg_buffer); // 现在我们得到了两个必要的东西： // 图片的尺寸信息: picture->image_info // 图片的RGB数据: picture->rgb_buf /************** 以上代码都是固定的套路 *********************/ add_link(picture); return 0; }