void  StretchColors(void* pDest, int nDestWidth, int nDestHeight, int nDestBits, void* pSrc, int nSrcWidth, int nSrcHeight, int nSrcBits)
{
 //參數(shù)有效性檢查
 //ASSERT_EXP(pDest != NULL);
 //ASSERT_EXP((nDestBits == 32) || (nDestBits == 24));
 //ASSERT_EXP((nDestWidth > 0) && (nDestHeight > 0));
 
 //ASSERT_EXP(pSrc != NULL);
 //ASSERT_EXP((nSrcBits == 32) || (nSrcBits == 24));
 //ASSERT_EXP((nSrcWidth > 0) && (nSrcHeight > 0));
 
 //令dfAmplificationX和dfAmplificationY分別存儲水平和垂直方向的放大率
 double dfAmplificationX = ((double)nDestWidth)/nSrcWidth;
 double dfAmplificationY = ((double)nDestHeight)/nSrcHeight;
 
 //計(jì)算單個源位圖顏色和目的位圖顏色所占字節(jié)數(shù)
 const int nSrcColorLen = nSrcBits/8;
 const int nDestColorLen = nDestBits/8;
 
 //進(jìn)行圖片縮放計(jì)算
 for(int i = 0; i<nDestHeight; i++)      //處理第i行
  for(int j = 0; j<nDestWidth; j++)   //處理第i行中的j列
  {
   //------------------------------------------------------
   //以下代碼將計(jì)算nLine和nRow的值,并把目的矩陣中的(i, j)點(diǎn)
   //映射為源矩陣中的(nLine, nRow)點(diǎn),其中,nLine的取值范圍為
   //[0, nSrcHeight-1],nRow的取值范圍為[0, nSrcWidth-1],
   
   double tmp = i/dfAmplificationY;
   int nLine = (int)tmp;
   
   if(tmp - nLine > 0.5)
    ++nLine;
   
   if(nLine >= nSrcHeight)
    --nLine;
   
   tmp = j/dfAmplificationX;
   int nRow = (int)tmp;
   
   if(tmp - nRow > 0.5)
    ++nRow;
   
   if(nRow >= nSrcWidth)
    --nRow;  
   
   unsigned char *pSrcPos = (unsigned char*)pSrc + (nLine*nSrcWidth + nRow)*nSrcColorLen;
   unsigned char *pDestPos = (unsigned char*)pDest + (i*nDestWidth + j)*nDestColorLen;
   
   //把pSrcPos位置的前三字節(jié)拷貝到pDestPos區(qū)域
   *pDestPos++ = *pSrcPos++;
   *pDestPos++ = *pSrcPos++;
   *pDestPos++ = *pSrcPos++;
   
   if(nDestColorLen == 4)
    *pDestPos = 0;
  }
}