DCT数字水印matlab

基于DCT数字水印算法的matlab实现如下所示：

M = 256; % 原图像长度
N = 32; % 水印图像长度
K = 8;
I = zeros(M, M);
II = zeros(K, K);
B = zeros(M, M);
Idct = zeros(K, K);
D = zeros(M, M);

% 读取原图像
I = imread('C:\Users\Administrator\Desktop\liu.jpg');
subplot(2,2,1);
imshow(I);
title('原图像');

% 读取水印图像
G = imread('C:\Users\Administrator\Desktop\niu.bmp');
subplot(2,2,2);
imshow(G);
title('水印序列');

% 嵌入水印
T = 1;
for m = 1:N
    for n = 1:N
        x = (m-1)*K + 1;
        y = (n-1)*K + 1;
        II = I(x:x+K-1, y:y+K-1);
        Idct = dct2(II);
        if x == 1 && y == 1
            alfa = 0.002;
        else
            alfa = 0;
        end
        B = Idct * (1 + alfa * mark(T));
        Bidct = idct2(B);
        I(x:x+K-1, y:y+K-1) = Bidct;
        T = T + 1;
    end
end

% 显示嵌入水印后的图像
subplot(2,2,3);
imshow(I);
title('嵌入后的图像');
imwrite(I, '嵌入后的图像.bmp');

% 相关性比较
figure;
for i = 1:50
    mark2 = randn(1024, 1);
    % 计算相关值
    c = (mark2' * mark) / sqrt(mark2' * mark2);
    stem(i, c);
    hold on;
end