Image watermarking using SVD
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I tired to write code to insert 256*256 image as watermark in a host image 256*256. I am using SVD in my algorithm. I just convert the original image to SVD and adding the watermark image(W) to the singular value as SM=S+aW. a is scaling factor. Then I do SVD for SM and select to singular value of SM to construct the watermarked image.
Please, kindly tell me if my the following code is correct.
The PSNR between original watermark and extracted watermark is very high (> 265 db). Is this value is acceptable?
The code:
%-------------------------
%Embedding
%-------------------------
clear;
clc
img= imread('lena2.tif');
img=imresize(img,[256 256]);
[M,N]=size(img);
img=double(img);
[Uimg,Simg,Vimg]=svd(img);
Simg_temp=Simg;
% read watermark
img_wat= imread('cameraman.tif');
img_wat=imresize(img_wat,[256 256]);
alfa= input('The alfa Value = ');
[x y]=size(img_wat);
img_wat=double(img_wat);
for i=1:x
for j=1:y
Simg(i,j) =Simg(i,j) + alfa * img_wat(i,j);
end
end
% SVD for Simg (SM)
[U_SHL_w,S_SHL_w,V_SHL_w]=svd(Simg);
Wimg =Uimg* S_SHL_w * Vimg';
figure(1)
imshow(uint8(img));
title('The Original Image')
figure(2)
imshow(uint8(img_wat));
title('The Watermark ')
figure(3)
imshow(uint8(Wimg));
title('The Watermarked Image')
%%%%%%%%%%%%%%%%%%%%%%%%%%%
%calculate image quality degradation after inserting watermark
%%%%%%%%%%%%%%%%%%%%%%%%%%%
mse=mean(squeeze(sum(sum((double(img)-double(Wimg)).^2))/(M*N)));
PSNR=10*log10(255^2./mse);
msg=sprintf('\n\n-------------------------\nWatermark by SVD PSNR=%fdB\n-----------------------------\n\n', PSNR);
disp(msg);
%--------------------------------------------------------------------------
% %%Extraction Part
% -------------------------------------------------------------------------
[UWimg,SWimg,VWimg]=svd(Wimg);
D_1=U_SHL_w * SWimg * V_SHL_w';
for i=1:x
for j=1:y
Watermark(i,j)= (D_1(i,j) - Simg_temp(i,j) )/alfa ;
end
end
figure(8)
imshow(uint8(Watermark));
mse=mean(squeeze(sum(sum((double(img_wat)-(Watermark)).^2))/(M*N)));
PSNR=10*log10(255^2./mse);
msg=sprintf('\n\n-------------------------\nWatermark by SVD PSNR=%fdB\n-----------------------------\n\n', PSNR);
disp(msg);
4 Comments
Huanhuan Wang
on 29 Jun 2016
[U_SHL_w,S_SHL_w,V_SHL_w]=svd(Simg);
this line is wrong. Simg is the sigular value, not a image.
U can try this way:
Wimg =Uimg* Simg * Vimg';
where, 'Simg' is the new sigular U got before.Then, U can abondon the code:Wimg =Uimg* S_SHL_w * Vimg';
Answers (1)
meenakshi
on 30 Aug 2011
no, normally the psnr must be between 20 to 45.in calculation of mse instead of squeeze use, mean.
1 Comment
DAVID KING
on 17 Jan 2016
If u have any query thn regarding ur project either mail at matlabprojects35@gmail.com or, https://www.facebook.com/MatlabProjects-909644652486619. Kindly Spread it to Help Others.
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