A Transform Domain Hardcopy Watermarking Scheme

Digital image watermarking is the process of encoding information into a digital image without deteriorating the visual quality of the image. Digital watermarking techniques are designed to withstand various attacks such as standard image processing operations, compression and geometric transformations. In this report we focus on watermarking of printed images and argue that this application requires specialized methods. Previous work relating to hardcopy watermarking applied standard digital watermarking schemes or suggested techniques that exploit the specific printing (i.e. halftoning) process. This work proposes a novel transform domain hardcopy watermarking technique that is independent of the halftoning process and is rather based on a noise model for the printing and scanning operations. The proposed scheme allows for blind watermark decoding, i.e. the encoder does not know the original image. It is image adaptable, to enhance the visual quality, and is tuneable on the trade-off between information embedding, rate, and visual quality.