问题描述
我需要在不使用 MATLAB 现有函数的情况下实现 3 LSB 水印。
我需要我的函数使用 3 LSB 获取 2 个图像,包括灰度和预制水印。
我尝试了以下方法,但是从新图像中减去原始图像的结果都是零,这意味着它们是相同的。
function [C] = Q2(image,watermark)
% clc;
% image=imread('moon.tif');
% watermark=imread('cameraman.tif');
[X,Y] = size(image);
rewatermark = imresize(watermark,[X,Y]); % resizing watermark to fit image
% iterate the 3 LSB of the watermark and set them to a copy of the original
% image 3 LSB
C = image;
for i = 1:X
for j = 1:Y
for k = 1:3
if(bitget(rewatermark(i,j),k) == 1)
bitset(C(i,k,1);
else
bitset(C(i,0);
end
end
end
end
subplot(1,3,1)
imshow(image);
title('Original');
subplot(1,2);
imshow(rewatermark)
title('Watermark');
subplot(1,3)
imshow(C)
title('Invisble watermarked');
set(gcf,'units','normalized','outerposition',[0 0 1 1]);
set(gcf,'name','Q2 - Results','numbertitle','off')
解决方法
代替 bitset(C(i,j),k,1)
,使用:C(i,j) = bitset(C(i,1)
除 OOP 编程外,MATLAB 不支持引用(或指针)。
执行bitset(C(i,1)
,不修改C(i,j)
的内容,将相关位设置为1,并返回修改后的值。
注意:
我建议起诉 rewatermark
的高位(位 6,7,8)而不是低位 1,2,3,主要是“噪音”(但这取决于您的目标)。
这是一个代码示例:
%function [C] = Q2(image,watermark)
clc;
image=imread('moon.tif');
watermark=imread('cameraman.tif');
[X,Y] = size(image);
rewatermark = imresize(watermark,[X,Y]); % resizing watermark to fit image
% iterate the 3 LSB of the watermark and set them to a copy of the original
% image 3 LSB
C = image;
for i = 1:X
for j = 1:Y
for k = 1:3
b = bitget(rewatermark(i,k+5); % Use the high bits 6,8 (instead of lower bits 1,3 that are mainly "noise")
C(i,b); % Set bit k to the value of b (1 or 0)
%if(bitget(rewatermark(i,k) == 1)
% bitset(C(i,1);
%else
% bitset(C(i,0);
%end
end
end
end
subplot(1,3,1)
imshow(image);
title('Original');
subplot(1,2);
imshow(rewatermark)
title('Watermark');
subplot(1,3)
imshow(C)
title('Invisble watermarked');
set(gcf,'units','normalized','outerposition',[0 0 1 1]);
set(gcf,'name','Q2 - Results','numbertitle','off')
reconstructed_rewatermark = bitshift(C,5);
imshow(reconstructed_rewatermark);title('reconstructed_rewatermark');