1 clear all;
 2 close all;
 3 clc;
 4 
 5 a=imread('lena.jpg');
 6 
 7 imshow(mat2gray(a))
 8 [m n]=size(a);
 9 a=double(a);
10 r=rank(a);
11 [s v d]=svd(a);
12 
13 %re=s*v*d';
14 re=s(:,:)*v(:,1:1)*d(:,1:1)';
15 figure;
16 imshow(mat2gray(re));
17 imwrite(mat2gray(re),'1.jpg')
18 
19 re=s(:,:)*v(:,1:20)*d(:,1:20)';
20 figure;
21 imshow(mat2gray(re));
22 imwrite(mat2gray(re),'2.jpg')
23 
24 re=s(:,:)*v(:,1:80)*d(:,1:80)';
25 figure;
26 imshow(mat2gray(re));
27 imwrite(mat2gray(re),'3.jpg')
28 
29 re=s(:,:)*v(:,1:150)*d(:,1:150)';
30 figure;
31 imshow(mat2gray(re));
32 imwrite(mat2gray(re),'4.jpg')