采用几何校正优化的轮廓波水印算法

针对目前的图像水印难以同时抵抗常规攻击和几 何攻击的不足,提出一种新的轮廓波 水印算法。水印嵌入阶段,该方法将宿主图像进行离散小波变换和非下采样轮廓波变换,并 将水印嵌入到熵值最大的高频子带,解决了将水印嵌入低频无法抵抗几何攻击及高频不能 很好抵抗滤波等常规攻击的问题。在水印嵌入前对嵌入区域进行加密处理,提高算法的安全 性。水印提取阶段,利用Zernike矩对含水印图像进行几何校正再进行提取,进一步提高了 算法的抗几何攻击能力。最后利用峰值信噪比和归一化系数对算法进行评价,验证算法的不 可感知性和鲁棒性。仿真实验结果表明,算法在不同的宿主图像和水印图像上均表现良好。 该算法在具有较好不可见性的基础上,除了对常规攻击具有很好的抵抗力,对几何攻击也具 有强鲁棒性,归一化系数(normalization coefficient,NC)均达到了0.99

Contourlet watermarking algorithm based on geometric correction optimization

In view of the fact that the current robust watermarking is difficult t o resist both conventional attacks and geometric attacks,a new contourlet watermarking algori thm is proposed. In this watermark embedding stage,the host image is transformed by discrete wav elet transform and non-subsampled contourlet transform,and the watermark is embedded into the high frequency subband with the maximum entropy,which solves the problems that embed ding the watermark in the low frequency can not resist geometric attacks and high frequen cy can not resist conventional attacks such as filtering.The embedded area is encrypted before th e watermark is embedded,which improves the security of the algorithm.In the watermark extract ion stage,the watermark is geometrically corrected and extracted by using Zernike moments,whi ch further improves the anti-geometric attack ability of the algorithm.Finally,the algor ithm is evaluated by peak signal-to-noise ratio and normalized coefficient to verify the impercepti bility and robustness of the algorithm.Simulation results show that the algorithm performs well on di fferent host images and watermark images.On the basis of good invisibility,the algorithm no t only has good resistance to conventional attacks such as filtering and noise,but also has str ong robustness to geometric attacks such as translation and rotation,and the normalization coefficient (NC) value is more tha n 0.99.