A robust content-based watermarking technique

Geometric transformations change the image pixel positions where the watermark is embedded. As a result, a copyright verifier fails to detect the watermark even though the watermark is present in the transformed image. The content-based watermarking schemes try to solve this problem by first dividing the image into many disjoint patches and then locating those patches with respect to the salient points of the image. Most of the existing content-based schemes are vulnerable to scaling and general affine transformations. They do not work well against high JPEG compression either. This paper presents a content-based blind watermarking scheme using corners. The proposed scheme achieves robustness against affine transformations and signal processing attacks by using triangular patch normalization and spread spectrum watermarking technique respectively.