一种小波和余弦变换组合域内鲁棒的自适应零水印算法

摘要

In order to overcome the limitation of the watermarked image quality degradation due to the some changes of the original image data when embedding watermark in the traditional digital watermarking schemes, a robust adaptive zero-watermarking algorithm based on the combined transforms of the Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT) is proposed. First, the original digital image is decomposed into the appropriate levels of DWT,and the DCT is applied to the obtained wavelet approximation sub-image, and then the DCT AC coefficients are selected adaptively in orders according to the size of the embedded digital watermark and the coefficient difference value. Finally,after the combination of the original binary character watermark and the binary key image which is obtained from comparing the selected DCT AC coefficients, the embedding of zero-watermark is realized by registering to the center of authentication. The results demonstrate that the proposed zero-watermarking algorithm not only ensures the watermarked image quality without distortion, but also has very good robustness against the conventional treatments (for example:noise addition, filtering, JPEG compression, rotation), and is better than the some reported zero-watermarking algorithms.%克服了传统数字水印方案在嵌入水印时要对原始图像数据进行一定修改从而导致嵌入水印图像质量下降的局限性,提出了一个基于离散小波变换和离散余弦变换组合域内鲁棒的自适应零水印算法.算法首先对原始数字图像进行适当层次的离散小波变换,并对得到的小波逼近子图进行离散余弦变换,然后依据待嵌入二值字符水印的大小和相应的系数差值要求自适应地顺序选取离散余弦变换交流分量系数,最后根据它们之间的大小关系构造出一个二值水印密钥并与一个二值字符水印处理后保存到注册机构完成零水印的嵌入.实验仿真表明,提出的零水印算法不仅确保了水印图像质量的无失真,而且对常规处理(例如:加噪,滤波,JPEG压缩,旋转)具有非常好的鲁棒性,优于一些报道的零水印算法.