void CScreenDlg::OnPaint()
{
	CClientDC dc(this); 
	// 获取屏幕DC
	HDC hScrDC = ::GetDC(NULL);
	// 得到屏幕分辨率  
	INT nHeight = GetDeviceCaps(hScrDC, VERTRES);
	INT nWidth = GetDeviceCaps(hScrDC, HORZRES);  
	// 创建屏幕DC的兼容DC
	HDC hMemDC1 = CreateCompatibleDC(hScrDC);
	// 创建屏幕兼容位图
	HBITMAP hBitmap1 = CreateCompatibleBitmap(hScrDC, nWidth, nHeight);
	// 把兼容位图选入兼容DC
	HBITMAP hBitmap2 = (HBITMAP)SelectObject(hMemDC1, hBitmap1);
	// 复制DC
	BitBlt(hMemDC1, 0, 0, nWidth, nHeight, hScrDC, 0, 0, SRCCOPY);
	// 显示
	BitBlt(dc.GetSafeHdc(), 0, 0, nHeight, nWidth, hMemDC1, 0, 0, SRCCOPY);
	::DeleteObject(hBitmap1);
	::DeleteDC(hMemDC1);
	__super::OnPaint();
}