anchor.diff:    lager:debug("compute rows workers finished"),
     EtsInfo = ets:info(FractalEts),
     lager:debug("ets info: ~p", [EtsInfo]),
  -  lager:debug("clean up ets?"),
   
     %% convert ets table data into rowdata for png
     RowData = ets_to_rowdata(FractalEts, Height, []),
  
positive.code: %% convert ets table into fractal row data suitable for png
  ets_to_rowdata(_FractalEts, 0, RowData) ->
    %% Height = zero  so done, return RowData
    %%     later feature - put save to file here if desired
    lager:debug("later feature - put save to file here if desired"),
    %%     later feature - clean up ets here
  
negative.code:       lager:error("wait_for_row timeout. Row = ~p",[Row]),
        erlang:error("wait_for_row timeout")
    end,
  
    %% iterate for next row
    NewRow = Row - 1,
  