bool DrawAlpha(Image* pBgImg, HWND hWnd)
{
   if (!::IsWindow(hWnd)) return false;

CWndDecorate wndDecor(hWnd);
   //wndDecor.SetAlpha((255 * 20) / 100);
   //wndDecor.ShowOnDesk();

RECT rcWnd;
   ::GetWindowRect(hWnd, &rcWnd);
   int nWid = rcWnd.right - rcWnd.left;
   int nHei = rcWnd.bottom - rcWnd.top;

HDC hdcTemp = ::GetWindowDC(hWnd);
   HDC hdcMemory = ::CreateCompatibleDC(hdcTemp);
   HBITMAP hBitMap = CreateCompatibleBitmap(hdcTemp, nWid, nHei);
   SelectObject(hdcMemory, hBitMap);

HDC hdcScreen = ::GetWindowDC(hWnd);
   POINT ptWinPos = {rcWnd.left, rcWnd.top};

Graphics graph(hdcMemory);
   Point points[] = {Point(0, 0),Point(nWid, 0),Point(0, nHei)};
   graph.DrawImage(pBgImg, points,3);

SIZE sizeWindow={nWid, nHei};
   POINT ptSrc={0,0};

DWORD dwExStyle = ::GetWindowLong(hWnd, GWL_EXSTYLE);
   if ((dwExStyle & 0x80000) != 0x80000)
   {
    ::SetWindowLong(hWnd, GWL_EXSTYLE, dwExStyle ^ 0x80000);
   }

CString strTitle;
   m_alWnd.GetWindowText(strTitle);

Gdiplus::Font   font(L"宋体",12,FontStyleBold,UnitPixel);
   StringFormat   strFormat;
   SolidBrush   brush(Color(0xff,0,0,0));

graph.DrawString(strTitle, -1, &font, PointF(32,30),&strFormat, &brush);

::UpdateLayeredWindow(hWnd, hdcScreen, &ptWinPos, &sizeWindow, hdcMemory, &ptSrc, 0, &m_alBlend, ULW_ALPHA);

graph.ReleaseHDC(hdcMemory);
   ::ReleaseDC(hWnd,hdcScreen);
   hdcScreen = NULL;
   ::ReleaseDC(hWnd,hdcTemp);
   hdcTemp = NULL;
   DeleteObject(hBitMap);
   DeleteDC(hdcMemory);
   hdcMemory = NULL;

return true;
}

CWndAlpha<CMainDlg> wndAl;

wndAl.InitAlpha(L"C:\\bg.png", NULL, rcMargin, true);
m_pMainWnd = wndAl.GetMainWnd();
wndAl.DoModal();