A Watermarking Scheme Based on Two-dimensional Wavelet Filter Parametrization

Abstract

In this paper, a parametrization of two-dimensional wavelet filter system is used as a method to protect wavelet-based watermarks against unauthorized detection. This system is developed in terms of a novel transformation-Shift Unitary transform (SUT) of Conjugate Quadrature filter (CQF). The commonly used wavelet filters are only special cases of this system. Based on this system, a watermarking scheme is described to embed watermark into low frequency sub-bands of wavelet transformation. We overcome degradation problem by performing median filtering to the lowest frequency sub-band of wavelet transform and embed watermark into visually insensitive locations. Experiments show this method is robust to compression,median-filtering etc.