后台截屏

HBITMAP GetWindowBitmap(HWND hWnd)  
{  
	typedef BOOL ( __stdcall *pPrintWindow )(HWND ,HDC ,UINT );  
    RECT rect;   
	HMODULE h;  
	h = LoadLibrary( "user32.dll" );  
	pPrintWindow p;  
	if( h )  
	{  
		p = ( pPrintWindow )::GetProcAddress( h, "PrintWindow" );  
	}  
	
    ::GetWindowRect(hWnd,&rect);  
	
    HDC hScrDC=::GetDC(hWnd);                            //创建屏幕DC  
    HDC hMemDC=CreateCompatibleDC(hScrDC);                //创建内存DC  
    HBITMAP bitmap=::CreateCompatibleBitmap(hScrDC,rect.right-rect.left,rect.bottom-rect.top); //创建兼容位图  
    HBITMAP OldBitmap=(HBITMAP)::SelectObject(hMemDC,bitmap);    //把位图选进内存DC  
	
    p(hWnd,hMemDC,0);    
	
	HDC d;  
	HWND hw;  
	hw = ::GetDesktopWindow();  
	d = ::GetWindowDC( hw );  
	::BitBlt( d, 0, 0, 200, 200, hMemDC, 0, 0, SRCCOPY );  
	
    ::SelectObject(hMemDC,OldBitmap);   
	
    ::DeleteDC(hMemDC) ;            //删除内存DC  
    ::ReleaseDC(NULL,hScrDC) ;    //释放屏幕DC  
	
    return bitmap;  
}