基于图像置乱和小波变换的零水印算法

Zero digital watermark algorithm based on image confusion and wavelet transforms

传统的数字水印方法在嵌入水印时都要对原始图像数据进行一定的修改导致嵌入水印图像的保真度下降.提出了一种基于仿射变换置乱与小波变换的零水印算法,该算法对嵌入的水印图像进行置乱,选择被嵌入图像的小波变换的低频子图与置乱的水印图像进行运算,对运算结果进行循环移位产生密钥图像。而小波变换的低频子图集中了图像的主要特征,所以该水印算法对各种攻击(例如:加噪,滤波,JPEG压缩,剪切)具有很高的鲁棒性,而且产生的水印为灰度图像而不是二值序列,具有很好的检测精度。仿真实验表明该算法的鲁棒性优于现有算法,而且在抗各种常见攻击方面性能良好。

The drawback ofthe conventional digital watermark methods is loss ofimage fidelity due to the fact that essential modification to the original image should be done in embedding digital watermarks. A new algorithm for zero digital watermarks based on image confusion and wavelet transforms is proposed. In the proposed algorithm, the watermark image is confused with the affine transform, and then the digital watermark information is obtained by combining the confused watermark image with the low frequency part of the wavelet transform result of the original image via logical binary operation and binary circular shift. The low frequency part of the wavelet transform results represents the major information ofthe image while noise occurs in the high frequency part ofthe wavelet transform results. Therefore the proposed algorithm is relatively robust in the presence of noise and presents high detection accuracy due to the fact that the watermark is a gray level image instead of a sequence of binary number. Experimental results show the superiority of the＇proposed method in comparison with some recent methods. It is also shown that the proposed method is relatively robust to some image degradation processes such as noise, cropping, filtering and JPEG compression etc.