Kindly Explain the shuffled procedure and how this code shuffle the pixel values?

A=[1 2 3 4 ; 5 6 7 8; 9 10 11 12; 13 14 15 16];

disp('Given Matrix is');

disp(double(A));

%/////////////////////////////////////////////////

[m,n]=size(A);

a = 3;

b = 3;

num_iter = 5;

for k=1:num_iter

for i=1:m

for j=1:n

r = mod([round((1-(a*(i^2))+j)),round((b*i))],[m n]);

S(i,j)=A(r(1)+1,r(2)+1);

end

end

A=S;

end

disp('Shuffled matrixx is');

disp(double(S));

%//////////////////////////////////////////

%%Reshuflle Imge

[m,n]=size(S_img);

a = 3;

b = 3;

num_iter = 5;

for k=1:num_iter

for i=1:m

for j=1:n

r1 = mod([round((1-(a*(i^2))+j)),round((b*i))],[m n]);

x1(r1(1)+1,r1(2)+1)=S_img(i,j);

%x(i,j)=x1(r(1)+1,r(2)+1);

end

end

S_img=x1;

end

disp('shuffled matrix is ');

disp(double(x1));

Answer 1

[Image Analyst]

I'm pretty sure that's the algorithm for Arnolds Cat Map:

https://en.wikipedia.org/wiki/Arnold%27s_cat_map

Attached is my demo.