Dot Diffusion with Nonlinear Thresholding to Hide Data in Halftoned Images

Image data hiding is the hiding of invisible patterns in an image without degrading its visual quality. The hidden pattern can be visualized by overlaying the original image with watermarked ones or by applying an extraction algorithm. If the hidden pattern is visualized using the overlaying method, it can also be visualized using a simple XNOR operation. In the case that hidden data is extracted by a specific algorithm, it is commonly called steganography. In this paper we propose a method called dot diffusion with nonlinear thresholding (DDNT) to embed hidden data in halftone images, where the hidden data can be extracted by overlaying original and watermarked images or by performing the XNOR process on these two images. The main advantage of this method is that the hidden pattern´s intensity can be adjusted by three parameters. The DDNT data hiding method 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