数字水印技术LSB算法MATLAB源代码

close all

clear all;

% save start time

start_time=cputime;

% read in the cover object

file_name='E:\Phd\My Paper\Second paper -- Experiment\Experiment\Cover and Secret Image\lena.bmp';

[cover_object,map]=imread(file_name);

% read in the secret image

file_name='E:\Phd\My Paper\Second paper -- Experiment\Experiment\Cover and Secret Image\hat.bmp';

[secret,map1]=imread(file_name);

secret1=secret;

% convert to double for normalization, then back again

secret=double(secret);

secret=fix(secret./2); %rounds the elements of A toward zero, resulting in an array of integers secret=uint8(secret);

% determine size of cover object

Mc=size(cover_object,1); %Height

Nc=size(cover_object,2); %Width

% determine size of secret object

Mm=size(secret,1); %Height

Nm=size(secret,2); %Width

% title the secret object out to cover object size to generate watermark

for ii = 1:Mc

for jj = 1:Nc

if (secret(ii,jj)>75)

watermark(ii,jj)=255;

else

watermark(ii,jj)=0;

end

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

if (watermark(ii,jj)==0)

watermarked_image(ii,jj)=bitset(watermarked_image(ii,jj),1,0); %Set bit at certain position

else

watermarked_image(ii,jj)=bitset(watermarked_image(ii,jj),1,1); %Set bit at certain position

end

end

end

% write the watermarked image out to a file

imwrite(watermarked_image,'lsb_watermarked.bmp','bmp');

%==================================Extraction=========================== ========================

% determine size of watermarked image

Mw=size(watermarked_image,1); %Height

Nw=size(watermarked_image,2); %Width

% use lsb of watermarked image to recover watermark

for ii = 1:Mw

for jj = 1:Nw

RecoveryWatermark(ii,jj)=bitget(watermarked_image(ii,jj),1);

end

end

% scale the recovered watermark

RecoveryWatermark=2*double(RecoveryWatermark);

%==================================================================== ===============================

%===========================SharpAttack================= SharpedWatermarkImage = watermarked_image;

H = fspecial('unsharp',0.001); %the alpha from 0.005 to 0.1 20 numbers sharpImage = imfilter(SharpedWatermarkImage,H,'replicate');

figure(6);

colormap(gray(256));

imshow(sharpImage);

title('sharp Image');