Clustered-Dot Halftone Watermark Using Phase Modulation

Abstract

Digital watermarking provides a solution for protecting the copyright of digital contents, and print-and-scan resilient data hiding finds important applications in document security. In this paper, we propose a clustered dot halftone watermarking algorithm based on phase modulation. The watermark region and the other region use the threshold matrix for halftoning at the two different screen angle. The watermark is detected by overlaying the model, with one of the screen angle. Mean filtering and median filtering is performed on the recovered watermark to improve the appearance, and watermark is pre-processed using Arnold transformation to eliminate the edges in the border of the watermark. Experiments show watermark can appear under smearing, cropping and pint-and-scan attacks.