Intelligent Modified Difference Expansion for Reversible Watermarking

A Reversible Watermarking (RW) using Difference Expansion (DE) algorithm plays an important role on content authentication for highly secured medical and military images. According to this algorithm, the least significant bit (LSB) of inter-pixel differences (between a pair of neighboring pixel) is used to embed secret data. It is seen that none of the DE works focuses on structural information retentions for the watermarked image at high embedding capacity. Moreover, security measure of the hidden data is not investigated under distortion constraint scenario. To this aim, a modification in DE is proposed that not only increase embedding space but also makes little change in structure and contrast comparison under similar luminance background. In our approach an image is partitioned into edge, smooth and texture region using computed gradient magnitude obtained through sobel’s operator followed by adaptive distortion control. Simulation results shown that, this simple yet effective modification leads to better security of the hidden data.