Example #1
0
///////////////////////////////////////////////////////////////////////////////////////////
//行压缩函数
//该函数是内部调用函数,如果你想要引用它,必须保证
//cinfo->inbuf填满有效数据 ,否则将不能得到正确的压缩数据
void jint_process_rows(jpeg_compress_info *cinfo) 
{  
  	int mn; //当前缓冲里的MCU
  	JSAMPLE *mcu_start;  
	int mcu_delta; 
  	JSAMPLE *pdata; 
	//颜色转换选择调用(这里只做RGB到YCrCb的转换)
	if(cinfo->in_color_space==JCS_RGB)
	jutl_cc_rgb2ycc(cinfo->inbuf,cinfo->inbuf_width*cinfo->inbuf_height);	
	//处理每个MCU数据,分割inbuf的数据到每个元件的dct表中,并降低每个元件的采样率
	mcu_start=&cinfo->inbuf[0];
	mcu_delta=cinfo->mcu_width*cinfo->num_comp*sizeof(JSAMPLE);
	for(mn=0;mn<cinfo->mcu_per_row;mn++)
	{
		//对于每个元件,降低采样率并保存到各个元件中
		int cn;//元件计数器
		for(cn=0;cn<cinfo->num_comp;cn++)
		{
			JSAMPLE *comp_start=(JSAMPLE*)(mcu_start+cn);
			//初始化采样间隔(sampledelta)数据指针
			int h_samp_delta=cinfo->max_h_factor/cinfo->comp[cn].h_factor*cinfo->num_comp*sizeof(JSAMPLE);
			int v_samp_delta=cinfo->max_v_factor/cinfo->comp[cn].v_factor*cinfo->num_comp*sizeof(JSAMPLE)*cinfo->inbuf_width;			
			//对于每个块(block)
			int bn;//块计数器
			int pn;//数据指针
			for(bn=0;bn<cinfo->comp[cn].num_dct_table;bn++)
			{
				//初始化块开始地址
				JSAMPLE *block_start=(JSAMPLE*)(comp_start+(bn%cinfo->comp[cn].h_factor)*DCTSIZE*h_samp_delta+(bn/cinfo->comp[cn].v_factor)*DCTSIZE*v_samp_delta);				
				DCTVAL *dct=(DCTVAL*)&cinfo->comp[cn].dct_table[bn];//dct表元素
				for(pn=0;pn<DCTSIZE2;pn++)//对于每个元素
				{				
					if(pn%DCTSIZE==0)pdata=(JSAMPLE*)(pn/DCTSIZE*v_samp_delta+block_start);
					dct[pn]=*pdata;
					pdata+=h_samp_delta;
				}
			}
		}//颜色元件处理循环结束
		mcu_start+=mcu_delta;		
		jint_process_mcu(cinfo);//处理当前MCU数据
	}
}
Example #2
0
void jint_process_rows(jpeg_compress_info *cinfo) 
{ 
  int mn; /* current mcu in buffer */
  JSAMPLE *mcu_start;				  //jsample 压缩样本
  int mcu_delta;
  JSAMPLE *pdata; //
 // JSAMPLE *pdata;
  /* Color convertion invoke select.
   * Note: We just implemente RGB -> YCrCb converte. 
   */						 //如果颜色空间为RGB格式,则通过加权平均值法转换为YUV格式
  if(cinfo->in_color_space==JCS_RGB)//RGB到YUV的变换	  
    jutl_cc_rgb2ycc(cinfo->inbuf,cinfo->inbuf_width*cinfo->inbuf_height);
  /* Process each of MCU data.
   * Separate the 'inbuf' data to each color component's dct table,
   * and 'Make' down sample for every component.
   */
  mcu_start=&cinfo->inbuf[0];
  mcu_delta=cinfo->mcu_width*cinfo->num_comp*sizeof(JSAMPLE);
  for(mn=0;mn<cinfo->mcu_per_row;mn++) 
  {
    /* For every color component.
     * Down sample and save to each color component.
     */
    int cn;  /* component counter */
    for (cn=0; cn<cinfo->num_comp; cn++) 
    {    
      JSAMPLE *comp_start = (JSAMPLE *)(mcu_start + cn);
      /* init data-point sample delta */
      int h_samp_delta = cinfo->max_h_factor / cinfo->comp[cn].h_factor 
                       * cinfo->num_comp * sizeof(JSAMPLE);
      int v_samp_delta = cinfo->max_v_factor / cinfo->comp[cn].v_factor
                       * cinfo->num_comp * sizeof(JSAMPLE) 
                       * cinfo->inbuf_width;
      
      /* for every block */
      int bn;  /* block counter */
      int pn;  /* point of data */
      for (bn=0; bn<cinfo->comp[cn].num_dct_table; bn++)
      {
        /* init block start address */
        JSAMPLE *block_start = (JSAMPLE *)(comp_start 
                + (bn%cinfo->comp[cn].h_factor)*DCTSIZE*h_samp_delta 
                + (bn/cinfo->comp[cn].v_factor)*DCTSIZE*v_samp_delta);
        /* dct table element */
        DCTVAL *dct = (DCTVAL *)&cinfo->comp[cn].dct_table[bn];
        /* for each element  */
        for (pn=0; pn<DCTSIZE2; pn++) 
        {
          
          if (pn % DCTSIZE == 0) 
          {
            pdata = (JSAMPLE *)(pn/DCTSIZE * v_samp_delta + block_start);
          }
          dct[pn] = *pdata;
          pdata += h_samp_delta;
        }
      }
    } /* End of color component loop */
    mcu_start += mcu_delta;
    /* Process current MCU data.
     */
    jint_process_mcu(cinfo);
    /* for example : call jint_process_mcu(cinfo) */
  }
}