clear all
close all
clc
c = imread('mandril_gray.bmp'); c=[c c; c c];
imshow(c)
message = 'Universityofmsila1';
Code_ascii = uint8(message);
suite_binaire = (dec2bin(Code_ascii,8))';
suite_binaire = suite_binaire(:);
N = length(suite_binaire);
b = zeros(N,1); %b is a vector of bits
for k = 1:N
    if(suite_binaire(k) == '1')
        b(k) = 1;
    else
        b(k) = 0;
    end
end
N=length(b);
s = c;
i1 = size(c,1);
j1 = size(c,2);
ii1=randperm(i1);
jj1=randperm(j1);
for k=1:N
    dd=s(ii1(k),jj1(k));
    LSB = mod(dd, 2);
    if LSB == b(k)
        s(ii1(k),jj1(k)) = c(ii1(k),jj1(k));
    else
        if(LSB == 1)
            s(ii1(k),jj1(k)) = c(ii1(k),jj1(k))-1;
        else
            s(ii1(k),jj1(k)) = c(ii1(k),jj1(k))+1;
        end
    end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Ajout du Bruit
% s = imnoise(s,'salt & pepper',0.08);
% s = imnoise(s,'gaussian',0,0.000001);
imwrite(s, 'stéganographie_image.bmp');
figure
imshow(s)
psnr= PSNR(c,s)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Décodage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

for k=1:N
    dd=s(ii1(k),jj1(k));
    b1(k)= mod(dd, 2);
end
pb1=(dec2bin(b1))';
dy=(reshape(pb1,8,N/8))';
fy=(bin2dec(dy))';
textString = char(fy);
disp(textString);