The present invention relates to the methods of estimation and recovering of
general affine geometrical transformations which were applied to data, extensible
to any other defined class of geometrical transformations, according to the preamble
of the dependent claims. The parameters of the undergone deformation are robustly
estimated based on maxima given by a parametric transform such as Hough transform
or Radon transform of some embedded information with periodical or any other known
regular structure. The main applications of this invention are robust digital still
image/video watermarking, document authentication, and detection of periodical
or hidden patterns. In the case of periodical watermarks, the watermark can also
be predistorted before embedding based on a key to defeat block-by-block removal attack.
