Correlation-based watermarking for halftone images

In many printer and publishing applications, it is desirable to embed data in halftone images for copyright control and authentication purposes. While intentional attacks on printed matters may not be likely, unintentional attacks such as cropping and distortion due to dirt or human writing/marking are likely. In this paper, we propose a novel halftone image watermarking method called Correlation-based Watermarking Error Diffusion (CWED) to embed a full-size, high-resolution and robust binary image in a single halftone image during halftoning while introducing minimal distortion. Since CWED uses the stochastic properties of halftone images to embed the watermark throughout the whole image, CWED is robust to cropping and distortion due to dirt or marking.