Robust transparent image watermarking system with spatial mechanisms
Abstract A very robust against JPEG compression, difficult for collusion attack, and transparent secret key digital watermarking system, which takes a spatial-domain approach, is presented in this paper. The unique watermark that consists of both the owner's logo and the user's licence number provides the ownership protection and traceability of illicit dissemination. The technique of block-oriented and modular-arithmetic–based watermark embedding and extraction achieves the robustness against image processing such as lossy compression, filtering, and cropping. The random perturbation of the pixels within the marked block as well as the unique and fused watermark information result in difference images with irregular-shape and uneven-luminance blobs, hence greatly increase the difficulty of collusion attack. Transparency is further fulfilled by means of embedding the information bits around but not on the exact edges of the features to avoid edge sharpening or smoothing, which effectively magnifies the contrast among the distributed images. The experimental results demonstrate that the proposed watermarking system is superior to Voyatazis and Pitas's scheme with respect to image processing, and is much more secure than the method of Cox et al.'s method.