Embedding Color Watermarks Into Halftoning Images Using Minimum-Distance Binary Patterns

This paper presents a half toning-based watermarking method. This method enables the embedding of a color image into a binary black-and-white halftone, while maintaining the image quality. The proposed technique is capable of embedding watermarks of three color channels into a binary halftone. To achieve high quality halftones, the method maps colors to halftone channels with homogeneous dot patterns which in turn use different binary texture orientations to carry the watermark. They are obtained by solving a minimization problem in which the objective function is the binary distance between the original binary halftone and the available patterns. To restore the color information, we scan the printed halftone image and compute the inverse information (considering the dot pattern). Using the mapped information, we restore the original color channels from the halftone images using a high-quality inverse half toning algorithm. Experimental results show that the method produces restorations with a superior quality than other methods found in the literature and increases the embedding capacity.