有关 matlab lsb图像隐写改进算法

完成了的第一步以及第四步，但不知如何进行图一的互补嵌入要求，希望得到指教

close all;
clear all;
clc
cover_object = imread('C:\Users\10601\Desktop\cover\lena.bmp');
secret = imread('C:\Users\10601\Desktop\cover\peppers.bmp');
[Mc,Nc] = size(cover_object);
[Ms,Ns] = size(secret);
for i=1:Ms
for j=1:Ns
if (secret(i,j)>=70)
watermark(i,j)=255;
else
watermark(i,j)=0;
end
end
end
watermark_image=cover_object;
if (Ms<=Mc && Ns<=Nc)
for ii=1:Mc
for jj=Ms
if (bitget(uint8(watermark(ii,jj)),1) == bitget(cover_object(ii,jj),1))
watermark_image(ii,jj)=cover_object(ii,jj);
else if (bitget(uint8(watermark(ii,jj)),1)==1 && bitget(cover_object(ii,jj),1)==0)
watermark_image(ii,jj)=cover_object(ii,jj)+1;
else if (bitget(uint8(watermark(ii,jj)),1)==0 && bitget(cover_object(ii,jj),1)==1)
watermark_image(ii,jj)=cover_object(ii,jj)-1;
end
end
end
end
end
else
fprintf('秘密图片过大');
end

你看看这个程序：
% Watermark Recovery

clear all;

% save start time
start_time=cputime;

% read in watermarked image
file_name='lsb_watermarked.bmp';
%file_name='_lena_std_bw.bmp';
watermarked_image=imread(file_name);

% 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
watermark(ii,jj)=bitget(watermarked_image(ii,jj),1);
end
end

% scale the recovered watermark
watermark=2*double(watermark);

% display processing time
elapsed_time=cputime-start_time,

% read in original watermark
%file_name='_copyright_large.bmp';
%orig_watermark=imread(file_name);

% scale and display recovered watermark
figure(2)
imshow(watermark,[])
title('Recovered Watermark')

%************************************************
%计算峰值信噪比子程序 　　%
%输入：Im_original 原始图像 　　
% Im_modified 修改过的图像 　　
% 输出：S 峰值信噪比 　
%注：此程序用来计算灰度图像的失真程度 　　
% ***********************************************
function S=PSNR(Im_original,Im_modified)
if(size(Im_original)=size(Im_modified))
error('错误，两个输入的图像大小不一致');
end
% ndims isrgb
if((ndims(Im_original) == 3)&&~(ndims(Im_modified) == 3))
[m,n]=size(Im_original);
A=double(Im_original);
B=double(Im_modified);
sumaDif=0;
%maxl=mn(max(A(:))^2);
maxl=mn255^2;
for u=1:m
for v=1:m
sumaDif=sumaDif+(A(u,v)-B(u,v))^2;
end
end
if(sumaDif==0)
sumaDif=1;
end
Si=maxl/sumaDif;
S=10*log10(Si);
else
error('错误，输入图像为彩色图像');
end
end

% Watermark Embeding

clear all;
clc;
% save start time
start_time=cputime;

% read in the cover object
file_name='lena.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);
disp('PSNR=');
disp(psnr);
% 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=watermark1256;
%message1=message1256;
figure(3)
imshow(watermark1,[])
title('the watermark embedded')
figure(4)
imshow(message1,[])
title('the original watermark')