this is the first part to hide image in image using lsb. how to get the messege from the cove ? i tried to get it but i coudn't ... please i want it in my study

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hudof najeeb 2016-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/316720-this-is-the-first-part-to-hide-image-in-image-using-lsb-how-to-get-the-messege-from-the-cove-i-tr

评论： Guillaume 2016-12-13

close all;  
imtool close all;  
clear;  
workspace;
cover = imread('pigs.tif'); 
message = imread('dpg.tif'); 
%display on screen the two images 
figure(1), imshow(cover); title('Cover Image'); 
figure(2), imshow(message);title('Message Image'); 
%change to double to work with addition below 
cover=double(cover); 
message=double(message); 
%imbed = no. of bits of message image to embed in cover image 
imbed=4; 
%shift the message image over (8-imbed) bits to right 
%messageshift=bitshift(message,-(8-imbed)); 
%show the message image with only embed bits on screen 
%must shift from LSBs to MSBs
messageshift=uint8(bitshift(message,-(8-imbed)));
showmess=uint8(messageshift); 
showmess=bitshift(showmess,8-imbed); 
figure(3),imshow(showmess);title('4 Bit Image to Hide'); 
%now zero out imbed bits in cover image 
coverzero = cover; 
for i=1:imbed 
coverzero=bitset(coverzero,i,0); 
end 
cove=uint8(coverzero);
%now add message image and cover image 
stego = imadd(cove,messageshift); 
figure(4),imshow(stego);title('Stego image'); 
%save files if need to
%4 bit file that was embedded = same as file extracted 
imwrite(stego,'stego22.tif');

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hudof najeeb 2016-12-13

i want the second part to get the message(original image) from cover image please

Guillaume 2016-12-13

By using bitshift with an offset of 4 on your message, you're destroying half of the bits of your message. It is therefore impossible to recover it.

Also, why is the message initially converted to double if you're then going to convert it (twice!) to uint8. Also, what is the purpose of showmess that is never used anywhere (and is just the initial message with bits 0:imbed set to 0)

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