Colored Image Steganography in Matlab

Question

I have made a steganography algorithm in matlab to hide colored image inside another colored image. The probelm is the extracted image isn't same as the original secret image.

The idea of algorithm is taking the pixel from secret image and split it into 4 groups of 2 bits, then put each 2 bits instead of the least significant 2 bits of cover pixel. This is the code below:

clear;
clc;
cover = imread('colored.jpg');
secret = imread('c4.png');

row = size(secret,1);
col = size(secret,2);
col = col -mod(col, 4);

if size(cover, 1) < row*4 || size(cover, 2) < col*4
    error('Cover image is too small to hide the hidden image.');
end

disp(size(secret));

for i=1:row
    for j=1:4:col
        for k=1:3
            sbyte = secret(i,j,k);
            sbyte = dec2bin(sbyte, 8);
            start=1;
            for l=j:j+3
                cbyte = cover(i,l,k);
                cbyte = dec2bin(cbyte, 8);
                seg = sbyte(start:start+1);
                cbyte(end-1:end) = seg;
                cbyte = bin2dec(cbyte);
                cover(i,l,k) = cbyte;
                start = start+2;
            end
        end
    end
end

imwrite(cover, 'stego_image.png');

disp('----------');

hidden = zeros(size(secret));


stego = imread('stego_image.png');

for i=1:row
    for j=1:4:col
        for k=1:3
            sbyte = '';
            for l=j:j+3
                cbyte = stego(i,l,k);
                cbyte = dec2bin(cbyte, 8);
                sbyte = strcat(sbyte, cbyte(end-1:end));
            end
            hidden(i,j,k) = bin2dec(sbyte);
        end
    end
end


disp(size(hidden));

hidden = uint8(hidden) .* secret;
imshow(hidden);

The output should be the same as origianl secret image but I got: hidden