Vehicle license plate detection algorithm based on color space and geometrical properties

Abstract

In this paper, an algorithm for vehicle license plate detection (VLPD) is proposed, to select automatically statistical threshold value in HSI color space. The proposed VLPD algorithm consists of two main stages. Initially, HSI color space is adopted for detecting candidate regions. According to different colored LP, these candidate regions may include LP regions; geometrical properties of LP are then used for classification. The proposed method is able to deal with candidate regions under independent orientation and scale of the plate. Finally, the decomposition of candidate regions contains predetermined LP alphanumeric characters by using position in the histogram to verify and detect vehicle license plate (VLP) region. In experiment more than 150 images were used, they were taken from the variety of conditions such as complex scenes, illumination changing, distances and varied weather etc. Under these conditions, success of LP detection has reached to more than 94%. © 2009 Springer Berlin Heidelberg.