anchor.diff:      make_png_from_data(Rows, ConfigMap).
   
   
  -make_png_from_data(Rows, ConfigMap) ->       % create a Png from block of fractal data
  +%% create a Png from block of fractal data
  +make_png_from_data(Rows, ConfigMap) ->
       %% initialize the png
       ThisPng = imagelib:startPng( ConfigMap ),
   
  
positive.code:     compute_fractal_data_file( DataFile,       % file where data is written
                          [],             % ThisRow starts empty
                          Width,          % XPix starts width and decrements to 1
                          XRealRight,     %% XR starts at right and decrements to by deltaX
                          DeltaX,
                          Width,          % width
                          Height,         % YPix starts height and decrements to 1
                          YImaginaryHigh, % YI starts at top and decrements by delta y
                          DeltaY,
                          Height,         % height
                          ConfigMap).    % map of parameters
  
negative.code: 
  -module(compute_fractal_data).
  -author("Duncan Sparrell").
  %% try to make simple fractal data 
  %% and then turn into color data 
  %% and then make image
  
  %% public API
  -export([
            compute_fractal_data/1,       % create a block of fractal data
            compute_fractal_data_file/1,  % create fractal data and write to file
            compute_fractal_data_file2/1, % create fractal data and write to file
            make_png_from_data/2,         % create Png from block of fractal data
            make_png_from_file/1          % create Png from file of fractal data
            ]).
  
  %% expose functions for test
  