Lossless data hiding for halftone images

With the development of image halftoning techniques and computer networks, a large quantity of digital halftone images are produced and transmitted in the Internet. Meanwhile, hiding data in images becomes a powerful approach for covert communications, copyright protection, owner announcement, content authentication, traitor tracing, etc. This chapter proposes two look-up table based methods to hide data in the cover media of halftone images. Both of them belong to lossless data hiding techniques, i.e., not only the secret data but also the original cover image can be accurately recovered in data extraction when the stego image is intact. Besides, an application example of the proposed method in lossless content authentication is illustrated. Furthermore, a data capacity enhancement strategy is introduced based on a statistical property of error diffused halftone image micro structure.