Hiding Data in Color Halftone Images using Dot Diffusion with Nonlinear Thresholding

Image data hiding is the hiding of invisible patterns in an image without degrading its visual quality. This hidden pattern can be visualized by overlaying the original image with watermarked ones. Also it can be visualized using a simple XNOR operation. In this paper we propose a method called dot diffusion with nonlinear thresholding (DDNT) to embed hidden data in halftone images and its modification to color halftone images which will be called CDDNT. The main advantage of this method is that the hidden pattern´s intensity can be adjusted by three parameters. Also it utilizes the inherent parallelism in dot diffusion halftoning method, although it suffers from its lower visual quality than some other halftoning methods such as error diffusion.