Vehicle License Plate Automatic Recognition System

Vehicle license plate automatic recognition is the important application of computer vision and pattern recognition in the intelligent transportation domain, and is one of the important parts in transportation management. It plays important roles in the project management of expressway, urban road and parking area etc. Its wide application will contribute to the process of the traffic mechanography of our country.Its measure is to deal with the inputted images, exploit license plate location character segmentation character recognition to extract the character strings, and express these strings in text form. Moreover the aim is to recognize the character for information management and safe guarantee.The key to license plate recognition is the license plate location. Observing 200 vehicle pictures, we can get the accurate license plate area via reducing the noise by graying only extracting the vertical edge. The difficulties in the character segmentation are the noise character conglutination and rupture etc. However, the paper makes full use of the prior knowledge of the license plate, combining the contrast stretching with the improved Bernsen algorithm for the binary, utilizing the Hough algorithm to correct the slant plate, and then segmenting character, finally employing bubble-method for single character to reduce noise. What's more, the method of character recognition takes an important part in the whole system, and the key technique lies in the matching of feature and classifier. Therefore, the paper puts forward an algorithm that makes the character in the same size, and it links the PCA and nearest neighbour algorithm to recognize the character. However it has perfect effect because it is a special nonlinear method as well as descends dimension.As a result, it proves that this recognition system can be relatively accurate to locate license plate and recognize characters, and the performance of the system is good. It shows that combined pretreatments and recognition techniques can improve the ability of recognition, so the algorithm mentioned in the article has a certain reference value for the actual application of vehicle license plate system.