Watermarking for Halftoned Images using Error Diffusion with Nonlinear Thresholding

Halftoning is the process of representing a gray-level image with a binary image. Image data hiding is the hiding of invisible patterns in an image without degrading its visual quality. In this paper we propose a method called error diffusion with nonlinear thresholding (EDNT) to embed hidden data in a halftone image such that the hidden patterns can be visually inspected when the images are overlaid. The hidden image can also be extracted by means of XNOR operation on watermarked and original halftone images