matlab代码实现水印嵌入和提取

以下是Matlab中实现水印嵌入和提取的简单代码示例：

%% 嵌入水印

% 读取原始图像和水印图像
img = imread('original_image.jpg');
watermark = imread('watermark_image.jpg');

% 转换为灰度图像
img_gray = rgb2gray(img);
watermark_gray = rgb2gray(watermark);

% 进行DCT变换
dct_img = dct2(img_gray);

% 将水印图像二值化
bw_watermark = imbinarize(watermark_gray);

% 选择嵌入位置和嵌入强度
% 这里以随机选择10个位置为例
idx = randperm(numel(dct_img));
num_watermark = sum(bw_watermark(:));
num_embedded = 0;
for i = 1:numel(idx)
    if num_embedded >= num_watermark
        break;
    end
    [r, c] = ind2sub(size(dct_img), idx(i));
    if bw_watermark(r, c) ~= 0
        % 嵌入强度为1
        dct_img(r, c) = dct_img(r, c) + 1;
        num_embedded = num_embedded + 1;
    end
end

% 进行IDCT变换
watermarked_img = idct2(dct_img);

% 显示和保存水印嵌入后的图像
imshow(watermarked_img);
imwrite(watermarked_img, 'watermarked_image.jpg');


%% 提取水印

% 读取水印嵌入后的图像
watermarked_img = imread('watermarked_image.jpg');

% 转换为灰度图像
watermarked_gray = rgb2gray(watermarked_img);

% 进行DCT变换
dct_watermarked = dct2(watermarked_gray);

% 提取嵌入的水印信息
extracted_watermark = zeros(size(watermark_gray));
num_extracted = 0;
for i = 1:numel(idx)
    if num_extracted >= num_watermark
        break;
    end
    [r, c] = ind2sub(size(dct_img), idx(i));
    if bw_watermark(r, c) ~= 0
        % 嵌入强度为1
        if dct_watermarked(r, c) > dct_img(r, c)
            extracted_watermark(r, c) = 1;
            num_extracted = num_extracted + 1;
        end
    end
end

% 反变换得到原始水印图像
extracted_watermark = uint8(extracted_watermark * 255);
imshow(extracted_watermark);
imwrite(extracted_watermark, 'extracted_watermark.jpg');

需要注意的是，这只是一个简单的示例代码，具体实现需要根据实际情况进行调整和优化。