车牌识别系统毕业论文
论文(设计)题目
车牌识别系统——定位
系统的设计与实现
院系名称
计算机科学与技术系
专业（班级）
计算机科学与技术
摘    要
车牌识别系统作为智能交通系统的一个重要组成部分，在交通监控中占有很重要的地位。车牌识别系统可分为图像预处理、车牌定位、字符识别3个部分，其中车牌定位作为获得图像的重要步骤，是后续的字符识别部分能否正确识别车牌字符的关键环节。车牌定位系统实现对进行定位的功能,即从包含整个车辆的图像中到车牌区域的位置，并对该车牌区域进行定位显示，将定位信息提供给字符识别部分。
在本文中作者分析出具有如下特征：（1）具有固定的长宽比；（2）车牌区域内部字符数目固定；（3）字符与背景之间存在很大的颜差别；（4）对于含有车牌信息的灰度图像，
其车牌区域边缘明显，灰度跳变大，相对于车牌以外区域，具有明显的特征等。所以，一般基于图像处理的车牌定位系统是通过分析的某些特征来进行定位的。
针对车牌本身固有的特征，本文首先介绍了在车牌定位过程中常用的几种数字图像处理技术：图像的二值化处理、边缘检测和图像增强等。其次介绍了现在常用的车牌定位方法，并对这些方法进行分析，总结出各种方法的优缺点，然后在此基础上提出采用带边缘检测的灰度图像行扫描投影方法对车牌进行定位，并使用VC++6.0编码实现车牌定位系统。最后对该系统进行了测试，测试结果表明该系统具有良好的人机交互方式，具有较高的识别正确率和较快的识别速度，对用户给定的待测图像能够迅速准确地进行的定位并将定位结果显示给用户，该系统具有一定的实用价值。
关键词：车牌定位，灰度图像，行扫描，投影

Abstract
As an important part of the Intelligent Transportation Systems, License Plate Recognition S
ystem plays an important role in traffic monitoring area. License plate recognition system can be divided into three parts, i.e., image pre-processing, license plate location and character recognition. The vehicle license plate location is an important procedure 汽车牌照which is used to obtain a license image. It is also the key of the following character recognition system which can identify the correct license plate characters. License plate location system can perform the vehicle license location function, i.e., finding the location of the vehicle license in the image containing the entire vehicle license plate, positioning the plate region and then demonstrating the location information on the computer screen which will be transferred to the character recognition system.
In this thesis, the author analyzes the vehicle license and finds that it has the following characteristics: (1) Fixed aspect ratio. (2) Fixed license plate characters number. (3) Great color difference between characters and background. (4) Obvious edge and great intensity change for grayscale images with registration information, and obvious characteristics compared with the outer plate region. Therefore, the majority of image-based positioning systems perform location function by analyzing some characteristics of the vehicle license.
According to the own inherent characteristics of license plate, this thesis introduces many commonly used digital image processing techniques in the location process of license plate: binary image processing, edge detection and image enhancement, and so on. Then, we introduce the commonly used methods of license plate location. Further, we analysis these methods and summarize their advantages and disadvantages. Moreover, we propose locating plate by using the gray-scale image projection and line scanning method with edge detection. This system was implemented by using the VC++ 6.0. Finally, the experimental results indicate that the system has a good human-computer interaction, a better identification rate and higher speed. For images provided by users, the system can quickly and accurately locate the vehicle license and display the location results to the users. Therefore, this system has some practical values.
Key words: license plate location, gray-scale images, line scan, projection