Re: Grabbing desktop image under a window

"AliR \(VC++ MVP\)" <AliR@online.nospam>
Tue, 06 Mar 2007 16:13:01 GMT
Hi Asm,

If you hide the window and then show it again you will disrupt the some
message like WM_MOVE. So your window will be very hard to move.

I did this using layered windows, it works pretty good, the only thing that
needs work is the flickering of the border. (NOTE: this will only work for
WinXP and above.)

BOOL CMagnifyDlg::OnInitDialog()

   SetWindowLong(m_hWnd,GWL_EXSTYLE,GetWindowLong(m_hWnd, GWL_EXSTYLE) |


   return TRUE;

void CMagnifyDlg::GetImage()
    //make window completely transparent
   CRect Rect;
   CDC *pDC = GetDesktopWindow()->GetDC();
   CDC MemDC;
   int Saved = MemDC.SaveDC();



   //bring the window back

void CMagnifyDlg::OnPaint()
   CPaintDC dc(this); // device context for painting

   CRect Rect;
   CDC MemDC;
   int Saved = MemDC.SaveDC();


"MrAsm" <> wrote in message


I would like to do some processing on a rectangular area of an image.
I would like to use a window in a way similar to a magnifier glass,
e.g. I would like to move the window onto the desktop, and process the
desktop image under the window's client area.

Could you please suggest me some ideas to implement this?

A trivial approach - but I think ugly and inefficient - I thought
would be:

1. Get window client area rect
2. Hide the window
3. Grab desktop sub-image corresponding to client area rect of point 1
4. Show the window
5. Show the processed image

Thanks for your suggestions,

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