Geometrically invariant and high capacity image watermarking scheme using accurate radial transform

Angular radial transform (ART) is a region based descriptor and possesses many attractive features such as rotation invariance, low computational complexity and resilience to noise which make them more suitable for invariant image watermarking than that of many transform domain based image watermarking techniques. In this paper, we introduce ART for fast and geometrically invariant image watermarking scheme with high embedding capacity. We also develop an accurate and fast framework for the computation of ART coefficients based on Gaussian quadrature numerical integration, 8-way symmetry/anti-symmetry properties and recursive relations for the calculation of sinusoidal kernel functions. ART coefficients so computed are then used for embedding the binary watermark using dither modulation. Experimental studies reveal that the proposed watermarking scheme not only provides better robustness against geometric transformations and other signal processing distortions, but also has superior advantages over the existing ones in terms of embedding capacity, speed and visual imperceptibility.