如何通过Twain协议扫描文件但不显示扫描的对话框

TW_USERINTERFACE twUI;
twUI.ShowUI = TRUE; //设置为FALSE就不出扫描设置对话框
twUI.hParent = (TW_HANDLE)m_hMessageWnd;
if(CallTwainProc(&m_AppId,&m_Source,DG_CONTROL,DAT_USERINTERFACE,MSG_ENABLEDS,(TW_MEMREF)&twUI))
{
      m_bSourceEnabled = TRUE;
      m_bModalUI = twUI.ModalUI;
}
else
{
     m_bSourceEnabled = FALSE;
     m_bModalUI = TRUE;
}