Draw Bitmap in a windows base on MFC

Draw Bitmap

void CMainFrame::DrawView(HBITMAP hbmp)
{
	ASSERT(hbmp != NULL);
	
	CView *pView = GetActiveView();
	ASSERT(pView != NULL);

	// pView->Invalidate(TRUE);


	CDC *pDC = pView->GetDC();

	pDC->SelectObject((HGDIOBJ)hbmp);

	//建立一个缓存设备上下文 
	CDC   m_MemDc; 
	m_MemDc.CreateCompatibleDC(pDC); 

	//选择位图 
	m_MemDc.SelectObject((HGDIOBJ)hbmp); 


	BITMAP   bm; 
	::GetObject(hbmp,   sizeof(BITMAP),   &bm); 
	//bm.bmWidth 
	//bm.bmHeight

	CRect winrect;
	pView->GetClientRect(&winrect);

	int nWidth = bm.bmWidth < winrect.Width() - 20 ? bm.bmWidth : winrect.Width() - 20;
	int nHeight = bm.bmHeight < winrect.Height() - 20 ? bm.bmWidth : winrect.Height() - 20;

	int left = (winrect.Width() -nWidth) / 2;
	int top = (winrect.Height() - nHeight) / 2;
	
	CRect rect;
	// 清屏
	CBrush   backBrush(RGB(255,   255,   255));         
	CBrush*  pOldBrush = pDC->SelectObject(&backBrush);    
	pDC->GetClipBox(&rect);
	pDC->PatBlt(rect.left,   rect.top,   rect.Width(),   rect.Height(),   PATCOPY);   
	pDC->SelectObject(pOldBrush);   



	// 画在屏幕上 
	pDC->StretchBlt(left,   top,       //左上角坐标 
					nWidth, nHeight,     //显示的宽和高 
					&m_MemDc,   //从缓存中获取 
					0,   0,       //从源位图的（0，0）坐标开始显示 
					bm.bmWidth, bm.bmHeight,
					SRCCOPY);   //将源位图拷贝至屏幕); 



}