基于Contourlet变换的抗几何攻击数字水印算法

针对小波变换在表示二维图像时的局限性,提出了一种抗几何攻击的数字水印算法。该算法先用混沌系列对水印信息进行加密,再对原始图像进行Contourlet变换,然后对分解后的子带进行分块计算,选择能量较大的分块并嵌入加密后的水印信息,最后经过Contourlet逆变换得到嵌入水印后的图像。实验结果证明：该算法不仅对常规图像处理具有很好的鲁棒性,同时对抵抗几何攻击也具有很好的鲁棒性。

Contourlet transform based digital watermarking algorithm against geometrical attack

For the limitation of the wavelet transform in expressing two-dimensional images,a digital watermarking algorithm against geometric attack is proposed.In this algorithm,the encryption for watermarking information is carried out with chaos series first,the original image is decomposed by Contourlet,and then the sub-blocks in a decomposed low-frequency sub-band image are calculated one by one.The sub-blocks with great energy are chosen to embed the encrypted watermarking information.At last,the watermarked image is obtained through the inversing transform of Contourlet.These results prove that the digital watermark embedded algorithm has a good robustness not only for processing the conventional images,but also for resisting the geometric attacks.