License Plate Recognition Algorithm Based On Digital Image Processing Technology

From the Industry revolution, the rapid development of the transportation has brought obvious convenience to human, but at the same time, the increasing number of all kinds of transportation tools especially vehicles leads to the severe environment and society pressure, the Intelligent Transportation System (ITS) is devised to alleviate the pressure.The Intelligent Transportation System can control and manage the transportation immediately by inspecting the transportation stream at real time, so it can make use of transportation establishments efficiently. The License Plate Recognition is the kernel function of this system, The License Plate Recognition can automatically provide vehicles inspecting, validation, registering and alarming, so it can be used in high way management systems, parking charging systems, uptown vehicle management systems and electronic police systems.This paper accomplished the study of the civil License Plate Recognition algorithm and design of the civil License Plate Recognition system. The system consists of three modules: (1) all-weather plate locating algorithm, first of all, to enhance the contrast of the car picture by preprocessing, and then to get the difference of the processed image and then reduce the math dimensions of the picture data, then to put gauss transform and wavelet transform on the data, after these steps, the plate is located in horizontal direction, and then reduce the math dimensions of this horizontal direction plate and put gauss filter on it, last step, put morphology dilating and eroding on it, finally the accurate position of the plate can be get. (2) Characters recognition algorithms. To recognize characters by adopting two levels algorithm based on noise model, the first level can recognize most of characters by extracting the periphery features of each character, the second level can recognize the left characters by math statistical method and template match method. (3) The software platform of License Plate Recognition, a software system coded by c/c++ languages is designed and accomplished, it integrates all of our algorithms, it provides convenient way to observe the algorithm results. Experiments have been conducted on 531 typical car images taken from various scenes and different conditions, the result showed that the rate of the plate locating achieves 95% and the rate of the recognition can achieves 94.6%.