lsb.m

lsb算法将水印图像按最不重要位(LSB)方法嵌入到载体图像中

%将水印图像按最不重要位(LSB)方法嵌入到载体图像中，在把水印从载体图像中提取出来
%注:整个算法分为水印嵌入部分和水印提取部分。

% 读入载体图像
file_name='lena.bmp';
cover_object=imread(file_name);
% 读入水印图像
file_name='_copyright.bmp';
message=imread(file_name);
message=double(message);
message=round(message./256);
message=uint8(message);
% 确定载体图像的大小
Mc=size(cover_object,1);
Nc=size(cover_object,2);
% 确定水印图像的大小
Mm=size(message,1);
Nm=size(message,2);
for ii = 1:Mc
    for jj = 1:Nc
        watermark(ii,jj)=message(mod(ii, Mm)+1,mod(jj, Nm)+1);
    end
end
watermarked_image=cover_object;
for ii = 1:Mc
   for jj = 2:Nc
       watermarked_image(ii, jj)=bitset(watermarked_image(ii, jj), 1, watermark(ii ,jj));
   end 
end
imwrite(watermarked_image,'lsb_watermarked.bmp','bmp');
% 计算已嵌入水印图像的PSNR
%psnr=PSNR(cover_object, watermarked_image),
% 显示已嵌入水印的图像 e
figure(1)
imshow(watermarked_image,[])
title('Watermarked Image')
file_name='lsb_watermarked.bmp';
watermarked_image=imread(file_name);
Mw =size(watermarked_image,1);
Nw =size(watermarked_image,2);
for ii = 1:Mw
   for jj = 1:Nw
       watermark(ii, jj)=bitget(watermark_image(ii, jj),1);
   end
end
watermark=256*double(watermark);
%显示提取的水印图像
figure(2)
imshow(watermark,[])
title('Recovered Watermark')