Code

How to use the matlab code?

Encoding

Import an image
Write the message you want to encode in the variable Message in rgbtransform.m
run rgbtransform.m

Decoding

Import the encoded image
run rgbitransform.m

rgbtransform.m

Type in the message we want to hide and import image
Divides the 3D Image Matrice into 3 2D Matrices, where each matrice correspond to the R,G,B of the Image
Divides the message into 3 parts
Run the dctransform code to hide messages in each images
Combine the 3 images to form one RGB Image and saves the file


Message = 'Type in the message here:';
Image = catc;

Ir = Image(:,:,1);
Ig = Image(:,:,2);
Ib = Image(:,:,3);

Mlen = length(Message);
Messager = Message(1:round(Mlen/3));
Messageg = Message(round(Mlen/3)+1:round(2*Mlen/3));
Messageb = Message(round(2*Mlen/3)+1:Mlen);

tIr = dctransform(Ir, Messager)/255;
tIg = dctransform(Ig, Messageg)/255;
tIb = dctransform(Ib, Messageb)/255;

finalimg = cat(3,tIr,tIg,tIb);

subplot(2,2,1); imshow(cat(3,Ir,Ig,Ib))
subplot(2,2,2); imshow(finalimg)

% imwrite(finalimg, 'C:\Users\jkim2\Documents\SigSys\Final Project\fftimage.jpg')

dctransform.m

Discrete Cosine Transform (DCT)
Fast Fourier Transform Shift (FFTshift)
Hide message length in the middle
Encode message in the hiding region
Inverse FFTshift
Inverse DCT
Return ecoded image

function t_img = dctransform(image_in, message)

% % %DCT transform, shift
D = dct2(double(image_in)); %DCT of image
Ds = fftshift(D); %make center low freq

% % %plot
% subplot(2,2,1);image(image_in);
% subplot(2,2,3);imshow(log(abs(Ds)),[]);

[M N] = size(D); 
ci = round(M/2)+1; 
cj = round(N/2)+1;

% % %Hiding Region
lr = round(M/5); 
hr = round(M/3);

% % %Message
mlen = length(message);

% % % Hiding the Message
m=1; 
r=0;

for (i=1:hr)
    for (j=1:hr)
        r = sqrt(i*i + j*j);
        if ((r > lr) && (r < hr))
            if (m <= mlen)
                Ds(i+ci, j+cj) = double(message(m));
                Ds(i+ci, -j+cj) = Ds(i+ci, j+cj); % copy over to each quadrant
                Ds(-i+ci, j+cj) = Ds(i+ci, j+cj);
                Ds(-i+ci, -j+cj) = Ds(i+ci, j+cj);
                m = m+1; 
            end; 
        end; 
    end; 
end;
Ds(1,1) = mlen;

t_img = idct2(ifftshift(Ds));

% % %plot tranformed
% subplot(2,2,3);image(t_img);
% subplot(2,2,4);imshow(log(abs(Ds)),[]);
end

rgbitransform.m

Import encoded message
Divides the 3D image matrice into 3 2D matrices, where each matrice correspond to the R,G,B of the image
Run the idctransform code to decode messages in each images
Combine the 3 decoded messages to get the message

Irgbt = finalimg; %transformed image

Irt = Irgbt(:,:,1)*255;
Igt = Irgbt(:,:,2)*255;
Ibt = Irgbt(:,:,3)*255;

idctransform(Irt)
idctransform(Igt)
idctransform(Ibt)

icdtransform.m

DCT
FFTshift
Get the length of the message encoded in the middle
Print the message decoded from the hiding region

function idctransform(It)

D2 = dct2(It); 
Ds2 = fftshift(D2); 

mlen2 = uint8(Ds2(1,1));

[M2 N2] = size(D2); 
ci2 = round(M2/2)+1; 
cj2 = round(N2/2)+1;

% % %Hiding Region
lr2 = round(M2/5); 
hr2 = round(M2/3);

m2 = 1;
r2 = 0;
music = [];
for (i=1:hr2)
    for (j=1:hr2)
        r2 = sqrt(i*i + j*j);
        if ((r2 > lr2) && (r2 < hr2))
            if (m2 <= mlen2)
                fprintf(1, '%c', char(uint8(Ds2(i+ci2, j+cj2))))
                m2 = m2 +1; 
            end; 
        end; 
    end; 
end
end