Research And Developing Of License Plate Automatic Recognition System

The application of automatic identification technology for license plate in intelligent transport system is the inevitable trend of development, and plays a very important role to the rapid development of the national economy.Automatic identification system consists of image processing module, plate positioning module, characters division module and characters recognition module, including follow-up application development. According to different modules, this paper researches and analyzes the existing theories and algorithms, and puts forward a practical solution scheme of application significance.1.In image processing module, we use weighted average method to gray the image because people have different sensitivity to different colors;the selection of threshold is critical in two- value process, the dynamic adaptive threshold method is used in this paper, and the results are satisfactory;edge extracting use Laplace;noise removing process we adapt the median filtering method;2. Plate positioning module includes rough positioning and careful positioning. In this paper we analyze plate sizes, types and colors to get different characteristics vector such as geometric characteristics, gray level distributional characteristics, projection characteristics and rank characteristics of characters, then find the position of plate with these characteristics;3. In characters division module, the division method of vertical projection in two-way is put forward. This method is based on the vertical projection of the cars plates, and is able to divide the characters accurately, advantageous for characters recognition of cars plates;4. This paper raises different methods to figures recognition and letters as well as characters recognition. Figures are recognized using the projection technology, while letters and characters are recognized by CC4 neural network, giving the same attention to accuracy and speed of recognition;5. For applications development, database design is a focus, large-scale or satellite-based systems apply to use Oracle database;SQL Server database is fit for small system like district management system.Based on the above principles and methods, with the development platform of VC++6.0, program, and produce automatic recognition software of license plate.