Consideration of digital watermark extraction from images attacked by geometrical approach

Abstract

Watermarking methods need the robustness against the various image processings. We are examining the tolerance of the watermarking to a geometrical approach. Since the synchronization information in the watermarked image attacked by the geometrical approach has been usually lost, it is difficult to extract the embedded watermark from the image. In this paper, we present a new approach for tolerant watermarking method against to geometrical attack. In this method, the synchronization of the position of watermark information is taken by inverse affine transformation to the attacked image. This method uses each of four corner point of two images of before attacks and after attacks to calculate the parameter of inverse affine transform.