A novel method to embed watermark in different halftone images: data hiding by conjugate error diffusion (DHCED)

In this paper, we propose a novel way called DHCED to hide invisible patterns in two or more visually different halftone images (e.g. Lena and Harbor) such that the hidden patterns would appear on the halftone images when they are overlaid. Conjugate error diffusion is used to embed the binary visual pattern in the two distinct halftone images. Simulation results show that the two halftone images have good visual quality, and the hidden pattern is visible when the two distinct halftone images are overlaid.