Three Phase Reversible Watermarking Using Improved Median Based Prediction

Abstract

Reversible watermarking is a lossless watermarking technique which allows the extraction of watermark as well as the recovery of original cover media at the receiver end for ensuring authentication and integrity verification of watermarked data. In this paper, a high capacity improved median based prediction three phase reversible watermarking scheme for grayscale images is proposed. The scheme predicts the candidate pixels using median of original neighboring pixels, which keeps magnitude of prediction errors relatively small. In this scheme, we propose several improvements over its preceding schemes employing median based prediction, which bring about changes in terms of both embedding capacity and perceptual quality. Furthermore, we have shown the efficient creation of location map that requires only single bit to test for overflow/underflow. The experimental results on some of the publicly available standard test images demonstrate the effectiveness of the proposed scheme. At the end, we compare our proposed scheme with the state-of-the-art schemes. The comparison results demonstrate that the proposed scheme has lesser distortion for different payload size.

Keywords: Watermark, Reversible Watermarking, Prediction Error Expansion (PEE),

Hash Function.