A three-dimensional curved-surface model can be estimated by using both two-dimensional outlines obtained from a piece of image photographed from the top and a restriction that the paper is rectangular. Then, only the three-dimensional distortion in the image can be corrected based on the obtained three-dimensional...http://www.google.co.uk/patents/US20020044681?utm_source=gb-gplus-sharePatent US20020044681 - Apparatus and method for correcting distortion of input image
