基于组合变换域的彩色图像大容量零水印算法

A large-capacity zero-watermarking algorithm for color images based on combined transform domain

针对现有大多数彩色图像零水印方案中水印嵌入容量小且抗几何攻击鲁棒性能不佳等问题,提出一种基于组合变换域和位平面分解的大容量鲁棒零水印算法。对彩色载体图像的R、G、B通道分别进行快速有限剪切波变换(FFST),并对变换后的各低频子带进行非重叠分块置乱,将置乱后的各子带的分块离散余弦变换(DCT)系数用于构造四元数离散余弦变换(QDCT)系数矩阵;在每个QDCT系数矩阵中选取两个低频系数,利用其各个实部和虚部的符号极性构造8个二值鲁棒特征矩阵;将经过正交拉丁方置乱加密后的灰度水印图像按位分解,把位分解后的8个二值位平面分别与以上二值鲁棒特征矩阵进行异或并重组得到灰度级认证零水印。此外,在水印检测前,采用ORB算法对待认证图像进行几何校正。实验结果表明,所提算法水印嵌入容量和安全性高,且对于常规非几何攻击和几何攻击均具有较强的鲁棒性。

In view of the small watermark embedding capacity and poor robustness against geometric attacks in most of the existing zero-watermarking schemes for color images,a robust zero-watermarking algorithm with a large capacity based on combined transform domain and bit-plane decomposition was proposed.Firstly,the R,G,and B channels of a color carrier image were respectively subjected to fast finite shearlet transform(FFST),and each lowfrequency sub-band after FFST was processed by non-overlapping blocking and scrambling.The block discrete cosine transform(DCT) coefficients of each sub-band after the scrambling were used to construct the quaternion discrete cosine transform(QDCT) coefficient matrices,and then two low-frequency coefficients were selected from each QDCT coefficient matrix.Eight binary robust feature matrices were constructed according to the sign polarities of the real parts and the imaginary parts from the above two coefficients.Finally,the gray-level watermark image scrambled and encrypted by the orthogonal Latin squares matrices was decomposed by bits.The eight binary bit-planes after decomposition were used for XOR operation with the above binary robust feature matrices and recombined to obtain the final gray-level authentication zero-watermark.In addition,before the watermark detection,the image to be authenticated was geometrically corrected by the oriented FAST and rotated BRIEF(ORB) algorithm.The experimental results show that the proposed algorithm has high watermark embedding capacity and security,and it is highly robust to both conventional geometric and non-geometric attacks.