Perspective rectification in vehicle number plate recognition using 2D-2D transformation of Planar Homography

Perspective rectification is an important part of Automatic Number Plate Recognition (ANPR) system. If the number plate is captured from non-orthogonal position, the recognition performance will be low due to perspective distortion on the number plate image. Planar Homography can be used to correct camera perspective to obtain clear and straight image of the number plate. Perspective rectification is performed by determining position of 4 corner points of the object in the image and finding the homography matrix that defines the movement of those corner points at new location. Experimental results show that the proposed method improves the recognition accuracy by 3% compared with conventional method without perspective rectification.