对话框透明，控件不透明（控件显示背景图）

    virtual BOOL OnInitDialog();
    afx_msg HBRUSH OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor);



ON_WM_CTLCOLOR()





BOOL CDlgXXX::OnInitDialog()
{
    CBCGPDialog::OnInitDialog();
    COLORREF maskColor = RGB(255, 255, 255);
    m_brush_.CreateSolidBrush(maskColor);

    LONG nExStyle = ::GetWindowLong(m_hWnd, GWL_EXSTYLE);
    nExStyle |= WS_EX_LAYERED;
    ::SetWindowLong(m_hWnd, GWL_EXSTYLE, nExStyle);
    SetLayeredWindowAttributes(maskColor, 128, LWA_COLORKEY); // 透明度范围是0～255

    CRect rtClient(0, 0, 22, 42);
    MoveWindow(&rtClient);
    m_btn_arrow_.MoveWindow(rtClient);
    m_btn_arrow_.m_nFlatStyle = CBCGPButton::FlatStyle::BUTTONSTYLE_NOBORDERS;
    m_btn_arrow_.m_bTransparent = TRUE;
    m_btn_arrow_.SetMouseCursorHand();
    if (m_nDir_ == 0)  //左边
    {
        m_btn_arrow_.SetImage(IDB_PNG_LEFT_CLOSE,IDB_PNG_LEFT_CLOSE_HOT,0,IDB_PNG_LEFT_CLOSE_HOT);
    }
    else if (m_nDir_ == 1)  //右边
    {
        m_btn_arrow_.SetImage(IDB_PNG_RIGHT_CLOSE,IDB_PNG_RIGHT_CLOSE_HOT,0,IDB_PNG_RIGHT_CLOSE_HOT);
    }

    return TRUE;
}

HBRUSH CDlgXXX::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
    HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);

    if(nCtlColor == CTLCOLOR_DLG)
    {  
        return (HBRUSH)(m_brush_.m_hObject);  
    }
    else if (nCtlColor == CTLCOLOR_BTN)
    {
        pDC->SetBkMode(TRANSPARENT);
        pDC->SetTextColor(RGB(0, 0, 0)); 
        return HBRUSH(GetStockObject(HOLLOW_BRUSH));
    }
    
    return hbr;
}




别忘了析构

CDlgXXX::~CDlgXXX()
{
    m_brush_.DeleteObject();
}