watermarking using dwt2 and psnr

how to calculate the psnr between the original image and the watermarked image? here is my code:

clc;clear all;close all; [filename1,pathname]=uigetfile('*.*','select the image'); %ouvrir une boîte de dialogue standard pour l'utilisateur image1=imread(num2str(filename1));

%img = imread('img1.bmp'); %lecture de l'image img = double(image1);%donne une double précision c = 0.00001; %Initialiser le poids du tatouage

figure,imshow(uint8(img)),title('Original Image'); [p q] = size(img);%retourner la taille de l'image

%Générer la clé diag=imread('oss.bmp'); diag=double(diag); %thresholdValue =70; %binaryImage = diag < thresholdValue; % Display the image. %figure,imshow(binaryImage, []); %caption = sprintf('Hidden Image Thresholded at %d', thresholdValue); %title(caption, 'FontSize', fontSize); figure,imshow(uint8(diag)),title('watermark'); imwrite(diag,'watermark.bmp','bmp'); N=input('entrer le niveau de décomposition: '); [Lo_D,Hi_D,~,Hi_R] = wfilters('bior3.5')%obtenir le filtre associé au ondelettes 5/3 [C,S] = wavedec2(img,N,'bior3.5') %calculer la transformée en ondelette discréte 2-D

[Lo_D,Hi_D,Lo_R,Hi_R] = wfilters('bior3.5') [C2, S2]= wavedec2(diag, N, 'bior3.5') [Lo_D,Hi_D,Lo_R,Hi_R] = wfilters('haar'); [ca,ch,cv,cd] = dwt2(img,Lo_D,Hi_D); %Exécuter le tatouage %y = [C;S] %w=[C2;S2] %Z = y + c*abs(y)*w %p=p/2^N;q=q/2^N y = [ca ch;cv cd]; Y = y + c*abs(y).*diag; p=p/2;q=q/2;

for i=1:p for j=1:q %nca(i,j) = Z(i,j); %ncv(i,j) = Z(i+p,j); %nch(i,j) = Z(i,j+q); %ncd(i,j) = Z(i+p,j+q); nca(i,j) = Y(i,j); ncv(i,j) = Y(i+p,j); nch(i,j) = Y(i,j+q); ncd(i,j) = Y (i+p,j+q); end end

%Afficher l'image tatouéeR wimg = idwt2(nca,nch,ncv,ncd,Lo_D,Hi_D,Lo_R,Hi_R); figure,imshow(uint8(wimg)),title('Watermarked Image'); imwrite(uint8(wimg),'watermarked.bmp','bmp'); %% PSNR (Peak Signal to noise ratio)

if (size(img) ~= size(wimg)) error('The size of the 2 matrix are unequal')

   psnr_Value = NaN;
   return; 
elseif (img == wimg)
   disp('Images are identical: PSNR has infinite value')

   psnr_Value = Inf;
   return;   
else

    maxValue = double(max(img(:)));

% Calculate MSE, mean square error. mseImage = (double(img) - double(y)) .^ 2; [rows columns] = size(wimg);

    mse = sum(mseImage(:)) / (rows * columns);

% Calculate PSNR (Peak Signal to noise ratio) psnr_Value = 10 * log10( 256^2 / mse);

end

%% correlation cor=corr2(img,wimg)

[Image Analyst]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup