B=eye(7);B(3,5)=100
A=floor(rand(7,7)*100)
A,A*B
A,B*A

n=8;e=.1;
A=64*rand(n,n)
B=(1-2*e)*diag(ones(n,1))+e*diag(ones(n-1,1),1)+e*diag(ones(n-1,1),-1);
B(1,n)=e;B(n,1)=e
image(A)


E=double(imread('einstein.gif'));size(E)
E=(230-E)/3; image(E)
n=60;E=E(11:70,:);size(E);image(E)
colormap gray
B=(1-2*e)*diag(ones(n,1))+e*diag(ones(n-1,1),1)+e*diag(ones(n-1,1),-1);
B(1,n)=e;B(n,1)=e

C=B^30*E*B^30;image(C)
for i=1:34 C=B\C/B; image(C), pause(0.3), end