lsb嵌入水印代码

% Name:        Chris Shoemaker
% Course:    EER - 280   -  Digital Watermarking
% Project:     Least Significant Bit Substitution
%            Watermark Embeding

clear all;

%  save start time
start_time = cputime;

%  read  in  the cover  object
file_name = ' _lena_std_bw.bmp ' ;
[cover_object,map] = imread(file_name);

%  read  in  the message image
file_name = ' key.bmp ' ;
[message,map1] = imread(file_name);
message1 = message;

%  convert to  double   for  normalization, then back again
message = double (message);
message = fix(message. / 2 );
message = uint8(message);

%  determine size of cover  object
Mc = size(cover_object, 1 );     % Height
Nc = size(cover_object, 2 );     % Width

%  determine size of message  object
Mm = size(message, 1 );             % Height
Nm = size(message, 2 );             % Width

%  title the message  object   out  to cover  object  size to generate watermark
for  ii  =   1 :Mc
     for  jj  =   1 :Nc
        watermark(ii,jj) = message(mod(ii,Mm) + 1 ,mod(jj,Nm) + 1 );
    end
end

%  now we  set  the lsb of cover_object(ii,jj) to the value of watermark(ii,jj)
watermarked_image = cover_object;
for  ii  =   1 :Mc
     for  jj  =   1 :Nc
        watermarked_image(ii,jj) = bitset(watermarked_image(ii,jj), 1 ,watermark(ii,jj));
    end
end

%  write the watermarked image  out  to a file
imwrite(watermarked_image, ' lsb_watermarked.bmp ' , ' bmp ' );

%  display processing time
elapsed_time = cputime - start_time,

%  calculate the PSNR
psnr = psnr(cover_object,watermarked_image,Mc,Nc),

%  display watermarked image
figure( 1 )
imshow(watermarked_image,[])
title( ' Watermarked Image ' )
figure( 2 )
imshow(cover_object,[])
title( ' original  image ' )
for  ii  =   1 :Mc
     for  jj  =   1 :Nc
        watermark1(ii,jj) = message1(mod(ii,Mm) + 1 ,mod(jj,Nm) + 1 );
    end
end
% watermark1 = watermark1 * 256 ;
% message1 = message1 * 256 ;
figure( 3 )
imshow(watermark1,[])
title( ' the watermark ' )
figure( 4 )
imshow(message1,[])
title( ' the watermark ' )