Towards adaptivity of image watermarking in polar harmonic transforms domain

A successful image watermarking method is identified by the high performance in a number of basic requirements such as robustness, imperceptibility, capacity and complexity. Enhancement could be achieved through an adaptive process that handles individually the embedded information to each coefficient. The specific need for adaptivity is justified through this work by a set of experiments applied to the traditional moment families (Zernike, Pseudo-Zernike, Tchebichef), where more optimum results are produced. The extensive study of Polar Harmonic Transforms' (PHTs) significance parameters (order, magnitude) along with the use of a generalized embedding strength calculation process, easily applied to circularly orthogonal transformations, leads to a promising solution of the adaptivity issue. Experimental results justify that the proposed image watermarking scheme clearly outperforms the compared methods in terms of robustness, capacity and complexity and promotes the traditional schemes to a next generation of moment-based image watermarking. (C) 2013 Elsevier Ltd. All rights reserved.