clc
clear
A=imread（‘lenna.bmp‘）;

imshow（A）;
figure
for?k=1:3
????for?j=1:128
????????B（1jk）=A（1jk）;
????????B（128jk）=A（128jk）;
????end
????for?i=1:128
????????B（i1k）=A（i1k）;
????????B（i128k）=A（i128k）;
????end