High capacity reversible data hiding based on histogram shifting for medical images

This paper presents a modified histogram shifting algorithm for reversible medical image watermarking to increase the hiding capacity. It is based on hierarchically dividing a cover image into smaller blocks for data embedding using the histogram shifting technique. To yield an optimal data hiding result, a technique for recursive looking-ahead estimation of the maximum data hiding volume at the lowest level of the block-division tree structure is used. The block divisions are performed and optimal division is selected based on the hiding capacity. A modified block division scheme is chosen for the medical images having large dark areas. In this method high data hiding capacity and high stego-image quality are achieved.