select
        accept Invert_Row(Row, Width: Integer) do
          Local_Row := Row;
          Local_Width := Width;
        end Invert_Row;
        for I in 1..Local_Width loop
          Picture_Pointer.all(Local_Row, I) := 255 - Picture_Pointer.all(Local_Row, I);
        end loop;
        accept Done;
      or
        accept Kill;
        exit;
      end select;