function THIPaintBox._OnMessage;
var P:TPoint;
begin
  Result := false;
  case Msg.message of
  WM_NCHITTEST:
    begin
      if not Control.Transparent then exit; 
      P.x := loword(Msg.lParam); P.y := hiword(Msg.lParam);
      if not ScreenToClient(Control.handle, P) then exit;
      if (P.x < 0)or(P.x >= bmp.width)or(P.y < 0)or(P.y >= bmp.height) then exit;
      if Bmp.Pixels[0,0]<>Bmp.Pixels[P.x,P.y] then exit; 
      Rslt := HTTRANSPARENT;
      Result := True;
      Exit;
    end;
  end;
  Result := Inherited _OnMessage(Msg,Rslt);
end;