Print-and-Scan Resilient Watermarking Based on Modulating the Averages of DCT Coefficients

Recently, the protection of the ownership information of digital images have received much attentions because illegal copying of digital multimedia has become much easier due to the advance of multimedia technologies. The ownership information is embedded as a watermark into the image for the purpose of asserting the copyright, hence, it should be very robust against various attempts to break or remove it. Among the various attacks to the watermark, the print-and-scan (PS) attack presents a difficult challenge because the PS attack not only alters the pixel values, but also changes the positions of image pixels. In this paper, we propose a PS-resilient watermarking algorithm which operates in the discrete cosine transform (DCT) domain. By analyzing the characteristics of the DCT coefficients under the PS attack, we modulate the averages of the DCT coefficients such that they are very robust against the PS attack. In addition, the image quality is also well preserved.