【作者】 张洁玮；

【导师】 曹杰；

【作者基本信息】 南京航空航天大学 ， 通信与信息系统， 2007， 硕士

【摘要】 随着信息技术和智能技术的发展,交通管理系统的信息化、智能化已成为发展的趋势。车牌识别系统(LPR)是智能交通系统(ITS)的核心组成部分,在现代交通收费管理系统中发挥着举足轻重的作用。近年来,对车牌识别系统中关键技术的研究已经成为智能交通领域的一个热点问题。本文对车牌识别系统中的图像预处理、车牌定位和字符分割等几大关键部分进行了比较深入、全面的论述,并对关键定位技术进行了深入的研究。本文采用基于颜色信息的综合车牌定位方法,车牌定位通过以下几个步骤来实现:首先是车牌粗定位,根据车牌区域横向积分投影连续性的特点,同时利用车牌白点数目占据主导的特点,用一个比估计的车牌小的矩形遍历整个边缘二值图,提取出大致的车牌范围。然后进行车牌底色的判断,因为在车牌图像预处理时已经保存了车牌颜色方面的信息,在此时分析出车牌的底色有利于下一步的车牌精确定位;其次是精确定位,根据车牌颜色的像素占该候选车牌区域所有像素的比例,采用行方向和列方向上的车牌定位技术,由此得到比较精确的车牌区域;然后采用结合Hough变换和垂直投影的方法对车牌进行倾斜校正,接着对字符图像进行去除边界处理,最后对字符图像进行切分。通过对采集于各种真实环境的图像进行实验,结果表明,本文所采用的方法能达到较好的车牌定位和字符分割效果,具有一定的鲁棒性和实时性。更多还原

【Abstract】 With the development of information technology and intelligence technology, the informatization and intelligentizing of traffic management is the trend. License Plate Recognition system (LPR) is the core of Intelligent Traffic System (ITS). It is very important in modern traffic management systems. In recent years, the study on the critical techniques for LPR has already become an important research field of scientific circles. In this paper we discuss the three parts of License Plate Recognition Systems: image pre-process, license plate location and character segmentation, and make a deep research on some important and key technology.A hybrid license plate location scheme is presented in this paper, which is mainly implemented as following several stages. At first, in the license plate roughly location stage, according to the continuity of transverse integral projection of the license plate region, and according to the number of white change points taking up a majority of the license plate, we use a rectangle to traverse the whole marginal-binary-image of the plate rage. After extracting the approximate license plate, judgment of the base color of the license plate is done, because the information of color is conserved when we do pre-treatment of the images. Second stage is accurately extracting the license plate. We use a method including horizontal and vertical operators to locate the license plate region; the pixel-rate is utilized to verify the real license plates which are the pixel of the plate color compare to the pixel of the candidate license plate color. In the last section, the slant correction of license plate is necessary to use the method combined with Hough transform and projection, so that the correspond plate region is present. Then we excise the border of the characters and segment them.Based on the experiments dealing with images taken under various real world conditions, the results prove that this proposed method can relatively locate license plate and segment characters. It shows that the performance of the system is promising, robust and timely.更多还原