Asked by Taha rassem
on 18 Feb 2011

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);

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Answer by meenakshi
on 30 Aug 2011

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

DAVID KING
on 17 Jan 2016

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## 4 Comments

## DAVID KING (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/1588-image-watermarking-using-svd#comment_335848

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.

## Nikesh (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/1588-image-watermarking-using-svd#comment_347301

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

## Huanhuan Wang (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/1588-image-watermarking-using-svd#comment_375887

## prerna gupta (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/1588-image-watermarking-using-svd#comment_434193

what is the value of alpha??

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