Invariant image watermarking using accurate Polar Harmonic Transforms

This paper proposes a geometrically invariant watermarking method based on highly accurate moments of Polar Harmonic Transforms (PHTs). Highly accurate, fast and numerically stable moments of PHTs are computed using a new simplified trigonometric formula. The proposed PHTs-based watermarking process is robust to geometric attacks. The proposed method consists of three main steps. In the first step, the Arnold scrambling algorithm is applied on a binary image. In the second step, accurate PHTs' moments of the original host image are computed. In the third step, a digital watermark is embedded by performing the quantization of selected PHTs' moments. The results of the numerical experiments ensure the validity of the proposed watermarking method. The proposed method shows a better visual imperceptibility and a better robustness to both geometric distortions and common signal processing attacks when compared with the existing moment-based watermarking methods.