A set of mutually watermarked halftone images
In this paper, we propose a method called, modified stochastic error diffusion (MSED), to hide an invisible binary visual pattern in a set of error diffused halftone images. MSED can embed a dithered watermark in multiple halftone images while preserving the visual quality of each halftone image. When any of these images overlapping with any others, the watermark will appear. In case that many of these image overlapped together, the contrast of watermark becomes clearer.