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%水印嵌入代码

M = 256;%原始图像长度

N = 32; %水印图像长度

K = 8;

I = zeros(M, M);

J = zeros(N, N);

BLOCK = zeros(K, K);

%显示原始图像

subplot(221);

I = imread('C:\Users\Rocky\Documents\MATLAB\cameraman.bmp');

imshow(I);

title('原始图像');

%显示水印图像

subplot(222);

J = imread('C:\Users\Rocky\Documents\MATLAB\matlab.bmp');

imshow(J);

title('水印图像');

%嵌入水印

temp = 1;

for p = 1 : N;

for q = 1 : N;

x = (p - 1) * K + 1;

y = (q - 1) * K + 1;

BLOCK = I(x: x + K - 1, y: y + K - 1);

BLOCK = dct2(BLOCK);

if J(p, q) == 0;

a = -1;

else

a = 1;

end

BLOCK(2, 1) = BLOCK(2, 1) * (1 + a * 0.01);

BLOCK = idct2(BLOCK);

I(x: x + K - 1,y: y + K - 1) = BLOCK;

end

end

%显示嵌入水印后的图像

subplot(223);

imshow(I);

title('嵌入水印后的图像');

imwrite(I,'watermarked.tif','tif');

%从嵌入水印的图像中提取水印

I = imread('cameraman.tif');

J = imread('watermarked.tif');

for p = 1 : N;

for q = 1 : N;

x = (p - 1) * K + 1;

y = (q - 1) * K + 1;

BLOCK1 = I(x: x + K - 1,y: y + K - 1);

BLOCK2 = J(x: x + K - 1,y: y + K - 1);

BLOCK1 = idct2(BLOCK1);

BLOCK2 = idct2(BLOCK2);

a = BLOCK2(1,1) / BLOCK1(1, 1) - 1;

if a < 0

W(p, q) = 0;

else

W(p, q) = 1;

end

end

end

%显示提取的水印

subplot(224);

imshow(W);

title('从含水印图像中提取水印');