渐进式jpg转换成基线式 jpg

最近在搞SSD202D平台的jpeg图片显示，发现progressive jpeg无法显示，于是就用libjpeg库progressive jpeg转换成baseline jpg

1、两种格式的区别

PEG有两种存储格式：baseline 和 progressive。Baseline JPEG 会在数据可用时，一行一行自上而下显示。Progressive JPEG会先显示模糊图片，然后逐渐清晰。

两种格式有相同尺寸以及图像数据，他们的扩展名也是相同的，唯一的区别是二者显示的方式不同。

Baseline JPEG

这种类型的JPEG文件存储方式是按从上到下的扫描方式，把每一行顺序的保存在JPEG文件中。打开这个文件显示它的内容时，数据将按照存储时的顺序从上到下一行一行的被显示出来，直到所有的数据都被读完，就完成了整张图片的显示。如果文件较大或者网络下载速度较慢，那么就会看到图片被一行行加载的效果，这种格式的JPEG没有什么优点，因此，一般都推荐使用Progressive JPEG

Progressive JPEG

和Baseline一遍扫描不同，Progressive JPEG文件包含多次扫描，这些扫描顺寻的存储在JPEG文件中。打开文件过程中，会先显示整个图片的模糊轮廓，随着扫描次数的增加，图片变得越来越清晰。这种格式的主要优点是在网络较慢的情况下，可以看到图片的轮廓知道正在加载的图片大概是什么。在一些网站打开较大图片时，你就会注意到这种技术。

那么如何利用libjpeg库来转换呢？

可通过分析JPEG文件格式，查找文件有SOF0 marker(baseline)还是SOF2 marker(progressive)

2、相关代码

这里使用的libjpeg_v9源码编译的库，相关代码已上传：

jpeg_v9_test_code.tar.gz-Linux文档类资源-CSDN下载

jpeg_to_baseline_jpeg.h

#ifndef _JPEG_TO_BASELINE_JPEG_H
#define _JPEG_TO_BASELINE_JPEG_H#ifdef __cplusplus
extern "C"
{
#endif#include <stdio.h>/*
1、检测图片文件是否为jpeg格式
2、如果图片是baseline格式的jpeg，不处理
3、如果不是baseline格式的jpeg，将其转换成baseline格式的jpeg
*/
int jpeg_to_baseline_jpeg(const char *file_path);#ifdef __cplusplus
}
#endif#endif // !_JPEG_TO_BASELINE_JPEG_H

jpeg_to_baseline_jpeg.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "jpeglib.h"
#include <setjmp.h>
#include "jpeg_to_baseline_jpeg.h"#define THIS_FILE "jpeg_to_baseline_jpeg.c"typedef struct jpeg_error_mgr_usr
{struct jpeg_error_mgr pub;jmp_buf setjmp_buffer;
}jpeg_error_mgr_usr_t;static char jpeg_last_error_buf[256] = {0};static void my_error_exit(j_common_ptr cinfo)
{printf("[%s::%s:%d] my_error_exit\n", THIS_FILE, __FUNCTION__, __LINE__);if (cinfo != NULL){jpeg_error_mgr_usr_t *error_ptr = (jpeg_error_mgr_usr_t *)cinfo->err;if (cinfo->err != NULL  && cinfo->err->format_message != NULL){memset(jpeg_last_error_buf, 0, sizeof(jpeg_last_error_buf)/sizeof(jpeg_last_error_buf[0]));(*(cinfo->err->format_message)) (cinfo, jpeg_last_error_buf);}if (error_ptr != NULL){longjmp(error_ptr->setjmp_buffer, 1);}}
}// 根据文件头判断是否是jpeg文件
static int is_jpeg_file(const char *file_path)
{int ret = -1;if (file_path == NULL || file_path[0] == '\0'){return ret;}unsigned short BMP = 0x4D42, JPEG = 0xD8FF, PNG[4] = { 0x5089, 0x474E };FILE *fp = NULL;short int i = 0;unsigned short pis[5] = { 0 };fp = fopen(file_path, "r");if (fp == NULL){printf("[%s::%s:%d] can not read %s\n", THIS_FILE, __FUNCTION__, __LINE__, file_path);return ret;}else{fread((void *)pis, 8, 1, fp);fclose(fp);}if (pis[0] == JPEG){printf("[%s::%s:%d] %s is JPEG file\n", THIS_FILE, __FUNCTION__, __LINE__, file_path);ret = 0;}return ret;
}int jpeg_to_baseline_jpeg(const char *file_path)
{int ret = -1;if (is_jpeg_file(file_path) != 0){return ret;}struct jpeg_decompress_struct out_cinfo = {0};struct jpeg_error_mgr_usr jpeg_err = {0};FILE * infile = NULL;JSAMPARRAY buffer;unsigned char *tmp = NULL;int row_stride = 0;unsigned char *output_buffer = NULL;unsigned int out_image_width = 0;unsigned int out_image_height = 0;int out_image_components = 0;J_COLOR_SPACE image_in_color_space = JCS_UNKNOWN;//打开指定图像文件infile = fopen(file_path, "rb");if (infile == NULL){printf("[%s::%s:%d] file %s open failed!!!\n", THIS_FILE, __FUNCTION__, __LINE__, file_path);return ret;}//绑定标准错误处理结构out_cinfo.err = jpeg_std_error(&jpeg_err.pub);jpeg_err.pub.error_exit = my_error_exit; // 自定义错误处理函数if (setjmp(jpeg_err.setjmp_buffer)){/*在正常情况下，setjmp将返回0，而如果程序出现错误，即调用my_error_exit然后程序将再次跳转于此，同时setjmp将返回在my_error_exit中由longjmp第二个参数设定的值1并执行以下代码*/printf("[%s::%s:%d] jpegLastErrorMsg:%s\n", THIS_FILE, __FUNCTION__, __LINE__, jpeg_last_error_buf);//out_cinfo.err->msg_code;jpeg_destroy_decompress(&out_cinfo);if (infile){fclose(infile);infile = NULL;}return ret;}//初始化JPEG解码对象jpeg_create_decompress(&out_cinfo);// 指定数据源jpeg_stdio_src(&out_cinfo, infile);//读取图像信息，即jpeg图片文件参数(void)jpeg_read_header(&out_cinfo, TRUE);// 如果原文件就是baseline格式的，就不需要转换if (out_cinfo.is_baseline == 1) // Baseline SOF0 encountered {if (infile){fclose(infile);infile = NULL;}jpeg_destroy_decompress(&out_cinfo);ret = 0;printf("[%s::%s:%d] picture %s baseline jpeg\n", THIS_FILE, __FUNCTION__, __LINE__, file_path);return ret;}printf("[%s::%s:%d] picture %s progressive jpeg\n", THIS_FILE, __FUNCTION__, __LINE__, file_path);//开始解压缩图像(void)jpeg_start_decompress(&out_cinfo);out_image_width = out_cinfo.output_width;out_image_height = out_cinfo.output_height;out_image_components = out_cinfo.output_components;image_in_color_space = out_cinfo.out_color_space;printf("[%s::%s:%d] out_image_components:%d, image_in_color_space:%d\n", THIS_FILE, __FUNCTION__, __LINE__, out_image_components, image_in_color_space);//分配缓冲区空间row_stride = out_cinfo.output_width * out_cinfo.output_components; // 每一行的步长buffer = (*out_cinfo.mem->alloc_sarray)((j_common_ptr)&out_cinfo, JPOOL_IMAGE, row_stride, 1);if (buffer == NULL){jpeg_destroy_decompress(&out_cinfo);if (infile != NULL){fclose(infile);infile = NULL;}ret = -1;return ret;}output_buffer = (unsigned char *)malloc(row_stride * out_cinfo.output_height);if (output_buffer == NULL){jpeg_destroy_decompress(&out_cinfo);if (infile != NULL){fclose(infile);infile = NULL;}ret = -1;return ret;}memset(output_buffer, 0, row_stride * out_cinfo.output_height);tmp = output_buffer;//读取数据while (out_cinfo.output_scanline < out_cinfo.output_height)  //scanline表示当前已读取行数，此循环依次读取图片所有数据{(void)jpeg_read_scanlines(&out_cinfo, buffer, 1);//将数据一行一行读取memcpy(tmp, *buffer, row_stride);tmp += row_stride;}//结束解压缩操作(void)jpeg_finish_decompress(&out_cinfo);//释放资源jpeg_destroy_decompress(&out_cinfo);// 关闭文件if (infile != NULL){fclose(infile);infile = NULL;}//变量定义struct jpeg_compress_struct input_cinfo;struct jpeg_error_mgr_usr input_jerr;FILE *outfile = NULL;JSAMPROW row_pointer[1];//指定目标输出图像文件outfile = fopen(file_path, "wb");if (outfile == NULL){if (output_buffer != NULL){free(output_buffer);output_buffer = NULL;}ret = -1;return ret;}//绑定标准错误处理结构input_cinfo.err = jpeg_std_error(&input_jerr.pub);input_jerr.pub.error_exit = my_error_exit;if (setjmp(input_jerr.setjmp_buffer)){/*在正常情况下，setjmp将返回0，而如果程序出现错误，即调用my_error_exit然后程序将再次跳转于此，同时setjmp将返回在my_error_exit中由longjmp第二个参数设定的值1并执行以下代码*/printf("[%s::%d] jpegLastErrorMsg : %s\n", __FUNCTION__, __LINE__, jpeg_last_error_buf);jpeg_destroy_compress(&input_cinfo);if (outfile != NULL){fclose(outfile);outfile = NULL;}if (output_buffer != NULL){free(output_buffer);output_buffer = NULL;}ret = -1;return ret;}//初始化JPEG对象jpeg_create_compress(&input_cinfo);// 指定输出对象jpeg_stdio_dest((struct jpeg_compress_struct *)&input_cinfo, outfile);//设定压缩参数input_cinfo.image_width = out_image_width;input_cinfo.image_height = out_image_height;input_cinfo.input_components = out_image_components;input_cinfo.in_color_space = image_in_color_space;jpeg_set_defaults((struct jpeg_compress_struct *)&input_cinfo);//此处设压缩比为70%，强制使用baseline格式jpeg_set_quality((struct jpeg_compress_struct *)&input_cinfo, 70, TRUE);//开始压缩jpeg_start_compress((struct jpeg_compress_struct *)&input_cinfo, TRUE);//写入数据while (input_cinfo.next_scanline < input_cinfo.image_height){row_pointer[0] = &output_buffer[input_cinfo.next_scanline*out_image_components*out_image_width];(void)jpeg_write_scanlines((struct jpeg_compress_struct *)&input_cinfo, (JSAMPROW *)&row_pointer, 1);}//压缩完毕jpeg_finish_compress((struct jpeg_compress_struct *)&input_cinfo);//释放资源if (outfile != NULL){fclose(outfile);outfile = NULL;}jpeg_destroy_compress((struct jpeg_compress_struct *)&input_cinfo);if (output_buffer != NULL){free(output_buffer);output_buffer = NULL;}return 0;
}/*
编译
arm-linux-gnueabihf-gcc jpeg_to_baseline_jpeg.c -o jpeg_tranfsfer -L. -ljpeg -Wl,-rpath=. -DTEST_ENA=1
*/
#if defined(TEST_ENA) && (TEST_ENA != 0)
int main(int argc, char* argv[])
{if (argc != 2){printf("args should be tow, such as: ./proc 1.jpg\n");return 0;}jpeg_to_baseline_jpeg(argv[1]);return 0;
}
#endif

3、代码编译运行结果

arm-linux-gnueabihf-gcc jpeg_to_baseline_jpeg.c -o jpeg_tranfsfer -L. -ljpeg -Wl,-rpath=. -DTEST_ENA=1

参考文献：

Baseline JPEG和Progressive JPEG的区别https://blog.csdn.net/kickxxx/article/details/8109356https://blog.csdn.net/kickxxx/article/details/8109356关于JPEG存储格式：baseline与progressivehttps://www.xuanfengge.com/jpeg-format-baseline-and-progressive.htmlhttps://www.xuanfengge.com/jpeg-format-baseline-and-progressive.html