利用jpeglib库进行图像压缩和解压缩

int Compress::compress_rgb_to_jpeg(unsigned char *jpeg_buffer, void *buffer, int width, int height, unsigned long* size, int quality) {  struct jpeg_compress_struct cinfo;  struct jpeg_error_mgr jerr;  JSAMPROW row_pointer;  FILE * outfile;   static int written;  unsigned char* out_buffer = NULL;  unsigned long out_size;  cinfo.err = jpeg_std_error (&jerr);  jpeg_create_compress (&cinfo);  /*if ((outfile = fopen("C:\\dest.jpg", "wb")) == NULL)  {  return 0;  }  jpeg_stdio_dest (&cinfo, outfile); */  //dest_buffer(&cinfo, jpeg_buffer, size, &written);    jpeg_mem_dest(&cinfo, &out_buffer, size);  cinfo.image_width = width;  cinfo.image_height = height;  cinfo.input_components = 3;  cinfo.in_color_space = JCS_RGB;  jpeg_set_defaults(&cinfo);   /*  cinfo.num_components = 1;  cinfo.jpeg_color_space = JCS_GRAYSCALE;*/  cinfo.num_components = 3;  cinfo.jpeg_color_space = JCS_YCbCr;  cinfo.data_precision = 8;  jpeg_set_quality (&cinfo, quality, TRUE);  jpeg_start_compress (&cinfo, TRUE);  char* path = (char*)buffer;  char temp = 0;  /*for (int i=0; i < width*height*3; i+=3)  {  temp = *(path+i);  *(path+i) = *(path+i+2);  *(path+i+2) = temp;  }*/  /*for (int i=0, j=0; j < width*height*3; i+=3, j+=4)      {          *(path+i)=*(path+j+2);          *(path+i+1)=*(path+j+1);          *(path+i+2)=*(path+j);      }  */  while (cinfo.next_scanline < height)   {  row_pointer = (JSAMPROW)buffer + cinfo.next_scanline*width*3;  jpeg_write_scanlines (&cinfo, &row_pointer, 1);  }  jpeg_finish_compress (&cinfo);  if (jpeg_buffer != NULL)  {   for(int i = 0; i < *size; i++)  {  jpeg_buffer[i] = out_buffer[i];  }  }  jpeg_destroy_compress (&cinfo);  if(NULL != out_buffer)    {        free(out_buffer);        out_buffer = NULL;    }  return 1 ;}int Decompress::Decompress_jpeg_to_rgb(unsigned char *rgb_buffer, void *jpeg_buffer, int width, int height, unsigned long jpeg_size){struct jpeg_decompress_struct cinfo;struct jpeg_error_mgr jerr;FILE * infile;JSAMPARRAY buffer;int row_stride;        //绑定标准错误处理结构cinfo.err = jpeg_std_error(&jerr);  //初始化JPEG对象jpeg_create_decompress(&cinfo);//指定图像文件/*if ((infile = fopen("C:\\sample.jpg", "rb")) == NULL){return;}jpeg_stdio_src(&cinfo, infile);*/jpeg_mem_src( &cinfo, (unsigned char *)jpeg_buffer, jpeg_size );//读取图像信息(void) jpeg_read_header(&cinfo, TRUE);//设定解压缩参数，此处我们将图像长宽缩小为原图的1/2//cinfo.scale_num=1;//cinfo.scale_denom=2;    cinfo.num_components = 3;cinfo.jpeg_color_space = JCS_YCbCr;cinfo.data_precision = 8;/*cinfo.out_color_space = JCS_RGB;cinfo.image_width = width;cinfo.image_height = height;*/ //开始解压缩图像(void) jpeg_start_decompress(&cinfo);//分配缓冲区空间row_stride = cinfo.output_width * cinfo.output_components;//printf("cinfo.output_width = %d\n",cinfo.output_width);//printf("cinfo.output_components = %d\n",cinfo.output_components);buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);//读取数据while (cinfo.output_scanline < cinfo.output_height){(void) jpeg_read_scanlines(&cinfo, buffer, 1);//output_scanline是从1开始，所以需要减1int line=cinfo.output_scanline-1;memcpy(rgb_buffer+line*row_stride,buffer[0],row_stride);}//结束解压缩操作(void) jpeg_finish_decompress(&cinfo);//释放资源jpeg_destroy_decompress(&cinfo);//fclose(infile);return 0;}