A watermark sharing scheme to halftone images with genetic algorithms

We propose a watermark sharing scheme to binary halftone images, which is extended from an image halftoning scheme using genetic algorithms (GAs). In addition to the conventional evaluation functions on gray-level precision and appropriate contrast near edges, we design and introduce an evaluation function on watermark appearance to the scheme and generate multiple binary halftone images shared in a watermark image through the solution search of the GA. Simulation results have shown that we can share a watermark to generate a halftone image in keeping a high image quality, and clearly decode the embedded watermark by overlapping these images optically.