image_name = mGetLeftImageFileList;
	   
zero_bin = zeros( 2^8, 2^8 );	   
	   
grey = 2^7;

Hu0_total =0;
for image_count = 2:2%1:size(image_name,1);
  image_file = deblank( image_name( image_count,: ) )
  image = pgmRead( sprintf( '../images/%s', image_file ));
  
  [ row_total, col_total ] = size( image );
  
  bin = zero_bin;
  for row = 1:row_total
    for col = 2:col_total
      bin_row_index = image( row, col-1 )+1;
      bin_col_index = image( row, col )+1;
      % current pixel determines column since 3D mesh puts column along "x" axis.
      % zero is not a valid index -> add 1
      bin( bin_row_index, bin_col_index ) = bin( bin_row_index, bin_col_index ) + 1;
    end
  end
  
  % Normalize to find pdf
  PDF = bin / sum( sum( bin ) );
  
if image_count == 2
   for m=1:4; for n=1:4;mesh2=mesh2+PDF(m:4:256,n:4:256); end; end
   mesh2=mesh2';
%  if image_count == 0 			% display joint histogram for first image
    % subplot( 2, 1, 1 );
%    mesh( PDF' );
surface( [1.5:4:255], [1.5:4:255], mesh2 );
    PDF_max = max( max( mesh2 ) );
    PDF_max = ceil( PDF_max*2000 ) / 2000;
    axis( [ 0 255 0 255 0 PDF_max ] );
    view( -10, 30 );
    grid on;
    xlabel( 'First pixel' );
    ylabel( 'Second pixel' );
    zlabel( 'Joint Probability Density' );
     title( image_file );
    drawnow;
  end

  % x*log(x) = log(x^x)
  PlogP = log( PDF.^PDF)/log(2);
  
  Hu0 = -sum( sum( PlogP ) )
  Hu0_total = Hu0_total + Hu0;

end



Hu0 = Hu0_total / size(image_name, 1 )

sprintf( 'Normalized to word length per pixel:' )

Hu0/2