数字水印是一种通过在数字媒体里嵌入秘密信息来保护知识产权的技术.由于在图像中嵌入数字水印后,会导致图像一定程度的失真,因此,近年来出现了一种新的零水印方法.针对数字水印的不可感知性和鲁棒性之间的矛盾问题,提出了一种基于混沌调制的图像零水印方法,即该方法是从原始图像或测试图像的小波变换系数中提取低频子带部分小波系数的特征作为水印,而所抽取的小波系数的位置则由混沌法随机生成.实验结果表明,此算法的不可觉察性很好,并对一些诸如中值滤波、JPEG压缩、附加高斯噪声、裁剪和旋转等各种图像处理攻击有较强的鲁棒性.该方法改变了传统的向原始图像中嵌入水印信息的做法,不仅其得到的水印图像是无失真的,而且在不知道混沌初值的情况下,不可能成功地提取特征水印.

In this paper, a chaotic modulation digital image zero-watermarking method is proposed. Select some low frequency wavelet coefficients of original or tested image and compute the character of the selected coefficients to create watermarking. The wavelet coefficients is randomly selected by the chaotic method. The experimental results show that the watermarking method is invisible and robust against some image processing such as median filtering, JPEG compression, additive Gaussian noise, cropping and rotation attacks and so on. This method changes the traditional doings that watermarking is embedded into images, and make the watermarked image distortion-free. If the initial value of chaos is unknown, the characteristic watermarking can not be extracted correctly.