Chapter 5 - Lossless Information Hiding in Block Truncation Coding–Compressed Images

Abstract

This chapter focuses on block truncation coding (BTC)–based lossless information hiding schemes. BTC [1] is a block-based spatial domain image compression technique for grayscale images. Its main idea is to quantize the pixels in each block into two levels while preserving certain statistical moments of small blocks of the grayscale image. The absolute moment BTC [2] was proposed as a special kind of BTC to preserve the mean and the first absolute central moment of a block. After BTC compression, each block can be represented by a bitplane together with a pair of means called higher mean and lower mean. All higher means comprise a higher mean table, whereas all lower means comprise a lower mean table. To embed information, we can modify either the BTC encoding stage or the BTC-compressed data according to the secret bits. For reversible information hiding, we commonly embed information in BTC-compressed data, i.e., we can embed data in bitplanes, or mean tables, or both.