Halftone Image Watermarking Based on the Binary Pseudo-Wavelet Transform

With halftone images widely used in books, magazines, printer outputs, and fax documents, it is desirable to embed data in halftone images for copyright protection, content authentication and tamper detection. This paper proposes a novel watermarking method for error diffused halftone images based on the binary pseudo-wavelet transform. We employ the binary pseudo-wavelet coefficients' distribution properties to embed data by modifying some highest frequency coefficients. Then the modified coefficients are inverse transformed into the spatial domain and meanwhile the watermarked image is obtained. Watermark extraction is the inverse process of watermark embedding. Experimental results show that this method is robust to attacks such as human marking and cropping, furthermore it achieves a good tradeoff between the high data capacity and the slight visual distortion.