MATLAB: What is number of iterations deciding factor in the following code

arnold's cat maparnolds transformcat mapno. of iterations in arnolds cat map

clc;
clearvars;
close all;
workspace;
fontSize = 33;
grayImage = imread('cameraman.tif');
subplot(1,2,1);
imshow(grayImage);
[rows, columns, numberOfColorChannels] = size(grayImage);
N=rows;
T=1.4938*N+40.8689;
disp(T);
t=0;
T2=ceil(T);
disp(T2);
c = T
iscram= grayImage;
while t<T2
  for i= 1 : rows
    for j= 1 : columns
      r = mod(i+j,N)+1;
      c = mod(i+(2*j)+1,N)+1;
      imscram(i,j)=iscram(r,c);
    end
  end
  t=t+1;
  fprintf('t = %f, T2 = %f\n', t, T2);
end
subplot(1,2,2);
imshow(imscram);
(1) why should we use linear approximation of arnolds cat map, T=1.4938N+40.8689?
(2) which denotes the number of iterations in the above code?
(3) Even if i change t<700 or t<4, the output i got is the same..and also there is no change/improvement in NPCR and UACI value…

Best Answer

After your fprintf() you need to add
iscram = imscram;
Otherwise you are just repeating the same work over and over again instead of doing multiple iterations of the transform.
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