A method of digital watermarking which can resist against local geometrical distortions such as random bending attack, global geometrical distortions as well as projective transforms, but does not necessary require the recovering of global affine transform or even the repetition of the same watermark...http://www.google.de/patents/US7664288?utm_source=gb-gplus-sharePatent US7664288 - Digital watermarking method robust against local and global geometric distortions and projective transforms
