摘要： 结合混沌序列的优良特性给出了一个简单有效的图像混沌置乱算法，提出了一个在未压缩灰度级水印数据量的情况下，基于调整载体图像DCT 块系数与其对应8 邻域块DCT 系数均值的关系，自适应嵌入水印信息的盲水印算法。实验结果表明，该算法对JPEG 压缩、裁剪等常见的图像处理操作有较好的鲁棒性，具有一定的实用性。

关键词: 离散余弦变换；混沌加密；灰度水印；盲提取

Abstract: More and more researchers focus on meaningful digital watermarking, especially gray-scale watermarking, because it has much good advantage but is hard to deal with. First, this paper gives a simple but effective chaotic transform encryption algorithm of image, and then presents a gray-scale blind watermarking technique operating on DCT domain, which automatically embeds watermarking information by adjusting the relationship of coefficients of selected DCT block with the mean of corresponding coefficients of DCT blocks around the selected DCT block. The experimental results show that the proposed algorithm is effective and robust to common image processing operations and some geometric distortions such as JPEG compression and cropping. So a conclusion can be made that the proposed technique is practical

Key words: Discrete cosine transformation; Chaotic encryption; Gray-scale watermarking; Blind extracting