VC实现不规则窗口

void CExampleDlg::SetupRegion(CDC *pDC)
{
CDC                     memDC;
CBitmap                &cBitmap=m_bmpDraw;
CBitmap*              pOldMemBmp = NULL;
COLORREF          col,colMask;
CRect                    cRect;
int                        x, y;
CRgn                    wndRgn, rgnTemp;
GetWindowRect(&cRect);
CPoint ptOrg=cRect.TopLeft();
BITMAP bmInfo;
cBitmap.GetObject(sizeof(bmInfo),&bmInfo);
CRect rcNewWnd=CRect(ptOrg,CSize(bmInfo.bmWidth,bmInfo.bmHeight));
memDC.CreateCompatibleDC(pDC);
pOldMemBmp = memDC.SelectObject(&cBitmap);
colMask=memDC.GetPixel(0,0);
wndRgn.CreateRectRgn(0, 0, rcNewWnd.Width(), rcNewWnd.Height());
for(x=0; x<=rcNewWnd.Width(); x++)
{
for(y=0; y<=rcNewWnd.Height(); y++)
{
col = memDC.GetPixel(x, y);
if(col == colMask)
{
rgnTemp.CreateRectRgn(x, y, x+1, y+1);
wndRgn.CombineRgn(&wndRgn, &rgnTemp, RGN_XOR);
rgnTemp.DeleteObject();
}
}
}
memDC.SelectObject(pOldMemBmp);
SetWindowRgn((HRGN)wndRgn, TRUE);
}