Precise 2-step segmentation of corrupted characters in License Plate Recognition applications

Image-based License Plate Recognition (LPR) algorithms are the core modules of many Intelligent Transportation Systems (ITS). Different algorithms and approaches have been proposed so far. All of these methods have the following three steps in common: License Plate Localization, Character Segmentation & Character Recognition. There are many real-world issues encountered during the design of each step, including different plate formats, time-variant illumination conditions and etc. To have a reliable operator-free system, all of these need to be overcome. One of such issues which is the main focus of this article and so far has not been addressed in any previous work is the presence of characters corrupted by misplaced rivets/screws. In this paper we present a simple, yet effective technique based on traditional pattern matching methods which when combined with modern character recognition techniques, can bring up the success rates of current systems closer to 100%.