C / C++ / MFC

void CxxxxxxDlg::OnPaint() 
{

    CPaintDC dc(this); // device context for painting

	if (IsIconic())
	{
		

		SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{

	CDC memDC;
	memDC.CreateCompatibleDC(NULL);
	CBitmap Bitmap;
	Bitmap.LoadBitmap(IDB_BITMAP_BACK);
	memDC.SelectObject(&Bitmap);
	
	CRect rect;
        GetClientRect(&rect);

	LPBITMAPINFOHEADER m_pBmInfoHeader;     
    
	UINT width  = (UINT) m_pBmInfoHeader->biWidth;
	UINT height = (UINT) m_pBmInfoHeader->biHeight; 

	dc.BitBlt(rect.left,
				rect.top,
				width,
				height,
				&memDC,
				0,
				0,
				SRCCOPY);
	

	CDialog::OnPaint();

	}

}