Senary huffman compression - A reversible data hiding scheme for binary images

Abstract

Over the past few years many studies have proposed reversible data hiding schemes, but few have been applied to binary images. Some studies have utilized spread spectrum, compression and binary operations methods to achieve the data hiding goal, but most of them suffered from poor visual quality, capacity and inability to extract the hidden data during recovery. The performance of existing methods also is unsatisfactory. Therefore, this paper proposes a reversible data hiding scheme for binary images: SHC (senary Huffman compression). SHC adopts the half-white and half-black pixels of 4×1 or 2×2 blocks of six types to increase visual quality. Moreover, SHC is senary instead of binary and becomes double senary as a compression unit to increase compression rate and secret hiding capacity. Experimental results show that recovered images are well within human visual perception and have PSNR(s) greater than 33, high secret hiding capacity for 1.1 secret bits / 2 bits, and an effective compression rate of over 17% on average. All results demonstrate that the scheme has advantages in reversible data hiding for binary images. © Springer-Verlag Berlin Heidelberg 2007.