MFC透明窗口

HCURSOR CMFCApplication2Dlg::OnQueryDragIcon()
{
    return static_cast<HCURSOR>(m_hIcon);
}

void CMFCApplication2Dlg::OnBnClickedButton1( )
{
    // TODO:  在此添加控件通知处理程序代码
    DWORD style = GetWindowLong( m_hWnd,GWL_EXSTYLE);
    style = WS_EX_LAYERED;
    SetWindowLong(m_hWnd,GWL_EXSTYLE,style);

    m_slider.SetRange(0,255);

}

void CMFCApplication2Dlg::OnHScroll(UINT nSBCode,UINT nPos,CScrollBar* pScrollBar)
{
    // TODO:  在此添加消息处理程序代码和/或调用默认值

    if (nSBCode==SB_THUMBTRACK)
    {
        SetLayeredWindowAttributes(NULL,//透明色

                                nPos,//透明度
                                LWA_ALPHA

                                );
    }

    CDialogEx::OnHScroll(nSBCode,nPos,pScrollBar);
}