车牌定位与字符分割的研究与实现

【作者】 杨阳；

【导师】 任明武；

【作者基本信息】 南京理工大学 ， 计算机应用技术， 2006， 硕士

【摘要】 进入新世纪，随着我国公路交通事业的快速发展，对智能交通系统的需求又进入新的阶段。车辆本身的信息，如车牌号，车主，养路费的征收情况等是车辆自动化管理的操作对象，而车牌识别是车辆信息的获取的最主要的手段。由此可见，车牌识别系统在智能交通领域的重要作用。 一个完整的车牌识别系统由车牌定位、字符分割和字符识别等单元组成，涉及面广。其中车牌定位和字符分割在整个系统中起着关键性作用，它们的处理结果直接影响整个系统的精确度，鉴于此本文研究的主要内容是车牌定位与字符分割的方法。 本文中研究了两种车牌的定位方法：第一种是基于连通域分析的车牌定位方法。在选定的阈值范围内二值化图像，穷举其连通域轮廓，借助链码计算连通域的形状参数，筛选轮廓形状并以过滤后的轮廓中心线确定车牌位置；第二种方法基于图像的垂直边缘特征，使用垂直方向的Prewitt梯度算子提取图像的垂直边缘，逐点以边缘点密度为衡量标准来优化边缘特征图像，最后用给定矩形面积内的击中率来确定车牌的位置。 本文在字符分割方面结合水平投影法和固定间距法，研究一种复合的分割方法，实验证明有较好地分割效果。 文中还讨论了基于Hough变换的车牌矫正方法，运用Hough变换检测车牌在垂直和水平方向上的倾斜角，较好地矫正了旋转和变形车牌。更多还原

【Abstract】 As coming along with the development of the highway traffic enterprise in the new century, the requirement of the Intelligent Traffic System (ITS) gets into a new level. The information about vehicle’s manufacturer, the owner, and the road maintenance cost and so on are the objects of the auto management of vehicle information, and one of the useful method to get these information is by Vehicle License Recognition System. Thus, Vehicle License Recognition system play a vital role in ITS.A Vehicle License Recognition system usually comprises three parts, vehicle license locating, character segmentation and character recognition. Vehicle license locating and character segmentation play the crucial role, which influence the precision of the whole system directly. Thus, this thesis mainly studies the vehicle license location and the character division.In this thesis, two vehicle licenses locating methods are studied. The first one is based on the analysis of region connectivity, which transforms image into binary images in continuous thresholds, getting all contours by tracing algorithm, and all the licenses plate liked regions are selected to compute the center position of the license plate. The second one is based on edge detection, by through extracting vertical edges to generate the density of edge points in a rectangle region, and the region with the most density can be considered as the position of license plate.In this thesis, area projection and fixed space gap are adapted to character segmentation, and experiments shows a good result.In this thesis, one method that uses the Hough Transform to correct the license plate is discussed also. By using the Hough Transform to compute incline angles of the plate in horizontal and vertical directions. The distort license plate can be corrected well.更多还原