A License Plate Location System for Cars and Motorcycles under Day and Night Condition

• Main Author: 許溥鑫
• Other Authors: 葉榮木
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/24630272750020151066

碩士 === 國立臺灣師範大學 === 機電科技研究所 === 95 === The increasing amount of vehicles is one of the common problems for most developed countries, and it is more critical for Taiwan which the population density is higher than lots of countries. According to the International Road Federation(IRF) census in 2005, in Taiwan, every family has 0.77 car in average, and there is a car got accident in every 79.81 cars. The above data totally reflect the problems made by the increasing numbers of vehicles. For nowadays the number of police far less than the vehicle, how to effectively manage the vehicle is an urgent issue. Today, most license plate location systems are applied for daytime image, which has enough brightness. However, they can’t be applied for dark and nighttime images. In this paper, we proposed a algorithm to locate license plate of cars and motorcycles under day and night conditions. At first, we calculated the value of average brightness of picture to distinguish day and night. After intensifying the picture contrast by a high boost filter, we apply the morphology gradient for detecting the plate candidate. Furthermore, we multiplied a constant to the average brightness value of images to be the threshold to image binarization, and checked the characteristic of plate appearance and calculated the three horizontal lines crossings to extract the correct plate position. The experiment results show that the average extraction rate and speed are 95.9%, 0.25sec at daytime and 83%, 0.36sec at nighttime. We believe the proposed method would be a robust license plate extraction system utilized in all day.