Hi, My current project is image steganography using lsb. I want the codes for finding both average and difference between two neighbor pixel values along wise columns for all rows. My codes are producing wrong answers.Can anyone help me with this?

warning off
clc
InImg1=imread('C:\peppers.jpg');
cover = imresize(InImg1,[512 512]);
cov=cover(:,:,1);
figure,imshow(cov)
title('Cover image');

InImg2=imread('C:\girl.jpg');
InImg2=imresize(InImg2,[512 512]);
sec=im2bw(InImg2);
%imwrite(sec,'s.jpg');
figure,imshow(sec)
title('Secret image');74

[covRows covColumns] = size(cov);
[secRows secColumns] = size(sec);

for row = 1:covRows
    for column = 1:covColumns-1

             l(row,column)=plus(cov(row,column)/2,cov(row,column+1)/2);
             n(row,column)=minus(cov(row,column),cov(row,column+1));

      end
  end

for row = 1:secRows
    for column = 1:secColumns-1
        even=mod(column,2);
        if (even~=0)
            stego(row,column)=plus(sec(row,column),l(row,column));
        else
            stego(row,column)=plus(sec(row,column),n(row,column));
        end
    end
end

figure,imshow(stego)
title('Stego image');