A Robust Watermarking Scheme Based Walsh-Hadamard Transform and SVD Using ZIG ZAG Scanning

Abstract

This paper presents a robust watermarking for still digital images based on Fast Walsh-Hadamard Transform (FWHT) and Singular Value Decomposition (SVD) using Zigzag scanning. In this paper, after applying Fast Walsh-Hadamard transform to the whole cover image, the Walsh-Hadamard coefficients are arranged in zigzag order and mapped into four quadrants-Q1, Q2, Q3, Q4. These four quadrants represent different frequency bands from the lowest to highest. The quadrant Q1 again divided into no overlapping blocks and in it the highest entropy block is selected and Singular Value Decomposition is applied and the singular values of that blocks is modified with the singular values of the Fast-Walsh-Hadamard transforms coefficients of watermark. A comparative analysis is carried with recents works on Hadamard Transform and results of the proposed method are found to be superior in terms of imperceptibility and robustness at the expense of increased computational complexity.