Affiliations: School of Computer and Information Technology, Liaoning Normal University, Dalian, China. wxy37@126.com, niupanpan3333@163.com
Correspondence:
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Abstract: Digital watermarking has been proposed as an effective technology of copyright protection and content authentication, yet up to now, research on the robust watermarking against geometric attacks is still a challenging task. This paper presents a novel robust watermarking algorithm in nonsubsampled shearlet transform (NSST) domain using quaternion polar harmonic transform (PHT) and least squares support vector regression (LS-SVR), which is a recently developed geometric correction algorithm for digital color image. The major innovative works of the proposed approach lie in that (1) the NSST is applied to embed the watermark, which can provide the image function with nearly optimal approximation and employ fully the properties of human visual system (HVS), (2) the robust 2D transform, namely quaternion PHT is introduced to represent the characteristics of color image, and (3) the novel synchronous correction method is proposed using the excellent LS-SVR and quaternion PHTs, which can accurately estimate the geometric distortions parameters. In our experiments, we applied the proposed method to the standard color image test dataset, and the experimental results demonstrate that the proposed algorithm is not only invisible, but also robustness against common signal processing operations and geometric attacks.
Keywords: Color image watermarking, geometric distortions, nonsubsampled shearlet transform, quaternion polar harmonic transform, least squares support vector regression
