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%%圖像水印的LSB算法子程序	
%%************************************************************************
%%將水印圖像按質(zhì)量不重要位（LSB）方法嵌入到載體圖像中，再把水印從載體圖像中提取
%%出來
%%注:整個算法分水印嵌入部分和水印提取部分。
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%%這里算法十分容易理解，嵌入就是將圖像最低位替換為水印信息，提取就是從最低位將信
%%息提取出來，使用了bitset（A1v）將A中最低位替換為v中替代信息及bitget（B1）將
%%B中最低位信息提取出來即是水印信息
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close?all;
clear?all;
clc;
cd?E:\matlab\lsb_algorithm?%設(shè)置地址

%這里1指代最低位平面（即LSB），若使用8，可以很明顯看到水印信息
bit_position=1;
%..................LSB水印嵌入算法...........................
%?讀入載體圖像
file_name=‘lena_256.bmp‘;
cover_object=rgb2gray（imread（file_name））;


%?讀入水印圖像
file_name=‘test2.bmp‘;
message=rgb2gray（imread（file_name））;
message=double（message）;
message=message./256;
messagec=uint8（message）;
message=messagec;


%?確定載體圖像大小
Mc=size（cover_object1）;
Nc=size（cover_object2）;


%?確定水印圖像大小
Mm=size（message1）;
Nm=size（message2）;

for?ii=1:Mc
???for?jj=1:Nc
?????????watermark（iijj）=message（mod（iiMm）+1mod（jjNm）+1）;
?????????%這里將watermark擴(kuò)大為Mc*Nc大小，有Mc*Nc/（Mm*Nm）塊重復(fù)
???????end
end
watermarked_image=cover_object;%構(gòu)建一個與原圖片相同大小的矩陣用于存儲結(jié)果
for?ii=1:Mc
???for?jj=1:Nc
	?????????watermarked_image（iijj）=bitset（watermarked_image（iijj）bit_positionwatermark（iijj））;
	end
end
imwrite（watermarked_image‘lsb_watermarked.bmp‘‘bmp‘）;

%?計算嵌入水印后圖像的PSNR
psnr=PSNR（cover_objectwatermarked_image）;
%?計算嵌入水印后圖像的SNR
snr=SNR（cover_objectwatermarked_image）;

%?顯示已嵌入水印的圖像
figure;
imshow（watermarked_image[]）;
title（‘Watermarked?Image‘）

%···············LSB水印提取算法················
file_name=‘lsb_watermarked.bmp‘;
watermarked_image=imread（file_name）;
Mw=size（watermarked_image1）;
Nw=size（watermarked_image2）;
for?ii=1:Mw
?????for?jj=1:Nw
?????????????watermark（iijj）=bitget（watermarked_image（iijj）bit_position）;
?????end
end
watermark=256*double（watermark）;

%顯示提取的水印圖像
figure;
imshow（watermark[]）
title（‘Recovered?Watermark‘）

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件?????196662??2011-08-02?11:11??lsb\lena_256.bmp

?????文件???????2420??2011-08-02?16:19??lsb\lsb_sub.m

?????文件??????66614??2011-08-02?15:58??lsb\lsb_watermarked.bmp

?????文件???????1945??2011-08-02?16:20??lsb\PSNR.m

?????文件????????104??2011-08-02?16:23??lsb\readme.txt.txt

?????文件???????1077??2011-08-02?15:40??lsb\SNR.m

?????目錄??????????0??2011-08-02?16:20??lsb

-----------?---------??----------?-----??----

???????????????268822????????????????????7