基于DOCT和SURF的立体图像零水印算法

Stereo image zero watermarking algorithm based on DOCT and SURF

针对目前大多数立体图像零水印方案抗几何攻击性能不佳的问题,提出一种基于离散八元数余弦变换(DOCT)和加速鲁棒特征(SURF)的盲检测立体图像零水印算法。首先对原始立体图像的左右视点在CIEXYZ空间下的共6个分量分别进行平稳小波变换(SWT);然后将以上获得的6个低频子带分别进行非重叠分块,用于构造对应位置上的八元数图像块,并在空域中直接计算所有八元数图像块DOCT后的DC系数;最后通过比较每一个八元数DC系数的模值和其整体均值间的大小关系构造鲁棒特征矩阵,并将其与经过量子密钥置乱和2D-LALM系统加密后的原始水印进行异或,即可得到最终的认证零水印。此外,零水印检测前,采用SURF方法对待认证立体图像进行几何校正。仿真结果表明,该算法对于常规攻击和几何攻击均表现出较强的鲁棒性能。

Aiming at the poor geometric attack resistance of most current stereo image zero watermarking schemes, a blind detection stereo image zero watermarking algorithm based on discrete octonion cosine transform(DOCT) and speeded up robust features(SURF) was proposed. Firstly, the stationary wavelet transform(SWT) was performed on six components of left and right views of the original stereo image under CIEXYZ color space. Secondly, the above six low-frequency subbands were divided into non-overlapping blocks to construct the octonion image blocks at the corresponding positions, and then the DC coefficients of all image blocks after DOCT were directly calculated in spatial domain. Finally, the robust feature matrix was constructed by comparing the magnitude relationship between the modulus of each octonion DC coefficient and their overall mean value. Then, the final zero watermark for authenticating was generated by executing XOR operation on the feature matrix and encrypted watermark that had been processed by quantum key scrambling and 2D-LALM system encrypting. In addition, the SURF method was employed to perform geometric correction on the stereo image to be authenticated before the zero-watermark detection. Experimental results show that the proposed algorithm displays better robustness against conventional attacks and geometric attacks.