图像格式转换之BMP格式转换为JPG格式

 // bmp2jpg.cpp : 定义控制台应用程序的入口点。
 //
 #include "stdafx.h"
 #include "jpeglib.h"
 #include "stdlib.h"
 #pragma comment(lib,"libjpeg.lib")
 #pragma pack(4)        //两字节对齐，否则bmp_fileheader会占16Byte

 /*图像bmp格式文件头结构*/
 struct bmp_fileheader
 {
     unsigned short    bfType;        //若不对齐，这个会占4Byte
     unsigned long     bfSize;
     unsigned short    bfReverved1;
     unsigned short    bfReverved2;
     unsigned long     bfOffBits;
 };

 /*图像bmp格式信息头结构*/
 struct bmp_infoheader
 {
     unsigned long    biSize;
     unsigned long    biWidth;
     unsigned long    biHeight;
     unsigned short   biPlanes;
     unsigned short   biBitCount;
     unsigned long    biCompression;
     unsigned long    biSizeImage;
     unsigned long    biXPelsPerMeter;
     unsigned long    biYpelsPerMeter;
     unsigned long    biClrUsed;
     unsigned long    biClrImportant;
 };

 FILE *input_file ; //输入bmp文件指针
 FILE *output_file; //输出jpg文件指针
 bmp_fileheader bmpFh;
 bmp_infoheader bmpIh;

 unsigned char *src_buffer;
 unsigned char *dst_buffer;

 /*读取图像bmp文件头结构*/
 void readBmpHeader()
 {
     /*读取输入bmp格式图像文件头*/
     fread(&bmpFh , sizeof(bmp_fileheader) ,  , input_file);

     /*读取输入bmp格式图像信息头*/
     fread(&bmpIh , sizeof(bmp_infoheader),  , input_file);
 }

 /*读取图像bmp数据*/
 void readBmpData()
 {
     fseek(input_file , bmpFh.bfOffBits,SEEK_SET);
     src_buffer = (unsigned char *)malloc(sizeof(unsigned char)*bmpIh.biWidth*bmpIh.biHeight*bmpIh.biBitCount/);
     if(NULL == src_buffer)
     {
         printf("malloc memory failed!\n");
         return ;
     }

     fread(src_buffer , sizeof(unsigned char)*bmpIh.biWidth*bmpIh.biHeight*bmpIh.biBitCount/, , input_file);

     /*将bmp数据读取到目标huffbuffer*/
     unsigned long width = bmpIh.biWidth ;
     unsigned long height= bmpIh.biHeight ;
     unsigned short depth= bmpIh.biBitCount/ ;
     unsigned char *src_point ;
     unsigned char *dst_point ;
     unsigned long i =  ;
     unsigned long j =  ;
     unsigned long rgb_index =  ;

     dst_buffer = (unsigned char *)malloc(sizeof(unsigned char)*width*height*depth);
     if(NULL == dst_buffer)
     {
         printf("malloc memory failed!\n");
         return ;
     }

     src_point  = src_buffer + width*depth*(height-);
     dst_point  = dst_buffer + width*depth*(height-);

     for(i =  ; i < height ; i++)
     {
         for(j =  ; j < width*depth ; j+=depth)
         {
             if(depth == )
             {
                 dst_point[j] = src_point[j];
             }

             if(depth == )
             {
                 dst_point[j+]=src_point[j+];

                 dst_point[j+]=src_point[j+];

                 dst_point[j+]=src_point[j+];
             }

         }

         dst_point -= width*depth ;
         src_point -= width*depth ;
     }
 }

 void synthese_jpeg()
 {
     struct jpeg_compress_struct cinfo;
     struct jpeg_error_mgr jerr;
     JSAMPARRAY buffer;

     unsigned long width=bmpIh.biWidth;
     unsigned long height=bmpIh.biHeight;
     unsigned short depth=bmpIh.biBitCount/;
     unsigned char *point;
     cinfo.err=jpeg_std_error(&jerr);        //libjpeg各种配置
     jpeg_create_compress(&cinfo);
     jpeg_stdio_dest(&cinfo,output_file);
     cinfo.image_width=width;
     cinfo.image_height=height;
     cinfo.input_components=depth;
     if (depth==)
         cinfo.in_color_space=JCS_GRAYSCALE;
     else
         cinfo.in_color_space=JCS_RGB;

     jpeg_set_defaults(&cinfo);
     jpeg_set_quality(&cinfo,,TRUE);    //中间的值为压缩质量，越大质量越好
     jpeg_start_compress(&cinfo,TRUE);

     buffer=(*cinfo.mem->alloc_sarray)
             ((j_common_ptr)&cinfo,JPOOL_IMAGE,width*depth,);
     point=dst_buffer+width*depth*(height-);
     while (cinfo.next_scanline<height)
     {
         memcpy(*buffer,point,width*depth);
         jpeg_write_scanlines(&cinfo,buffer,);
         point-=width*depth;
     }

     jpeg_finish_compress(&cinfo);
     jpeg_destroy_compress(&cinfo);
 }

 int main()
 {
     input_file=fopen("E:/test_pic.bmp","rb");
     if(NULL == input_file)
     {
         printf("open input file failed!\n");
     }
     output_file=fopen("E:/save_pic.jpg","wb");
     if(NULL == output_file)
     {
         printf("open output file failed!\n");
     }

     readBmpHeader();
     readBmpData();
     synthese_jpeg();
     fclose(input_file);
     fclose(output_file);

     free(src_buffer);
     free(dst_buffer);

     return ;
 }