Image watermarking using SVD

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);

[DAVID KING]

If u have any query thn regarding ur project either mail at [e-mail] or, https://www.facebook.com/MatlabProjects-909644652486619. Kindly Spread it to Help Others.

[Nikesh]

You should use correlation value not psnr to compare your embedded and extracted watermark

[Huanhuan Wang]

[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';

[prerna gupta]

what is the value of alpha??

Answer 1

[meenakshi]

no, normally the psnr must be between 20 to 45.in calculation of mse instead of squeeze use, mean.

[DAVID KING]

If u have any query thn regarding ur project either mail at [e-mail] or, https://www.facebook.com/MatlabProjects-909644652486619. Kindly Spread it to Help Others.