Data hiding in dot diffused halftone images

In this paper, we propose two halftone image watermarking methods. Data Hiding by Conjugate Dot Diffusion (DHCDD) and Data Hiding by Dual Conjugate Dot Diffusion (DHD-CDD). DHDCDD is an improved method of DHCDD. Both of these two methods can embed a secret pattern into two halftone images. When the two halftone images are overlaid, the secret pattern will be revealed. Compared to the recent method Noise Balanced Dot Diffusion, the experimental results show that the proposed methods are better in both Correct Decoding Rate and the visual quality of the revealed hidden pattern.