Digital images watermarking robust to print & scan for electronic evidence

In this paper, we explore the property of pixel value distortion and present a watermarking scheme robust to this distortion. From the investigation on the noise property of the print-and-scan process, we find that the smooth blocks get less distorted during this process. Watermark embedded in these blocks is probably more robust to the print-and-scan distortion. However, protecting the texture blocks from distortion is also necessary because the watermark extractor within this blind watermarking scheme also uses these texture blocks. For this reason, we design the noise adding operation to compensate the print-and-scan distortion to the texture blocks. In addition, the watermark extractor also affects the whole system performance, so we use the multiple-vote operation to enhance the robustness of water extractor. The rules of the multiple-vote operation are specially designed based on the property of the print-and-scan distortion.