what is the meaning of the following code ?

Following code is for retrieving image from stego image in image steganography. Can anyone please tell me meaning of it ?

function Retrive_Callback(hObject, eventdata, handles)
global l;
h=mod(l,2);
p=zeros(1000,1000);

for x=1:1000
    for y=1:1000
        if(h(x,y)==1)
            p(x,y)=255;
        end
    end
end

s=im2bw(p);
axes(handles.axes4);
imshow(s);
grid on;

Answer 1

[Sebastian Körner]

the code semes to have some errors in it but i think the idea of your code is :

create a 1000x1000 matrix with zeros, replacing some zeros with 255 (all values in a line from top left corner to bottom right corner of the matrix)

format the matrix to a image and show the image

[Gayatri B]

Ohk, I'll check for errors. Thank You !

Answer 2

[Image Analyst]

p is just 255 * h. And s just thresholds p back to 0 or 1, which is just the original h. So all that code is unnecessary.

Replace with

function Retrive_Callback(hObject, eventdata, handles)
global l;
h=mod(l,2);
axes(handles.axes4);
imshow(h, []);
grid on;

By the way, you reversed x and y. Matrices are indexed (y, x) NOT (x,y) because the first index is the y, or row, value, not the column value.

[Gayatri B]

Okay, Thank you !