DATA PROCESSING APPARATUS AND METHOD

摘要

A data processing apparatus registers an image which has been encoded with a two-dimensional water mark pattern. The water mark comprises for each frame of the image a water mark frame pattern of water mark blocks, the water mark pattern comprising a plurality of regions. Each region of the pattern includes one water mark block selected from a predetermined set of possible water mark blocks in accordance with a key sequence. The key sequence provides a predetermined sequence of selected water mark blocks to form the water mark pattern of each frame to provide a predetermined sequence of water marked frames. The data processing apparatus comprises a block match processor operable to generate block match probabilities comprising for each region of a current frame of the water marked image a probability surface of possible distortion vectors for each possible water mark block of the set of possible water marked blocks which may have been added to that region of the image frame. A water mark block prior probability calculator operable to form block prior probabilities, a distortion probability calculator operable to form a spatial prior probability surface for each region of the current image frame from the block prior probabilities and the block match probabilities, providing a probability distribution of distortion vectors for the region, and a mark of distortion processor operable to form an estimate of a distortion vector for each region from the adapted spatial prior probabilities. Accordingly, distortion in a water marked image can be detected and then removed with out a need to refer to an original copy of the image.