这个问题问了好多次，怎么没有人回答啊！

CDC *drawDC =  new CDC;
CDC *gtempDC =  new CDC;
CDC *tempDrawDC = new CDC;gtempDC->CreateCompatibleDC(&clientDC);
drawDC->CreateCompatibleDC(&clientDC);
tempDrawDC->CreateCompatibleDC(&clientDC);HBITMAP GBitmap = m_Image->MakeBitmap(gtempDC->GetSafeHdc());
drawDC->SelectObject(GBitmap);
tempDrawDC->StretchBlt(-px,-py,nWidth,nHeight,drawDC,0,0,m_Image->GetWidth(),m_Image->GetHeight(),SRCCOPY);pdc->StretchBlt(0,0,sWidth,sHeight,tempDrawDC,0,0,sWidth,sHeight,SRCCOPY);
delete tempDrawDC;
delete drawDC;
delete gtempDC;pdc是OnDraw中传递过的pDC；tempDrawDC作为pdc的源不知为什么显示出来的是空的，但直接用drawDC作为pdc的源，则可以定确显示.请大家帮帮忙，在线等！