License Plate Localization from Vehicle Images: An Edge Based Multi-stage Approach

Abstract

Abstract- Automatic license plate recognition (ALPR) system for vehicles is a challenging area of research due to its importance to a wide range of commercial applications. The first and the most important stage for any ALPR system is the localization of the license plate within the image captured by a camera. Variety of techniques has already been reported for localization of license plate and recognition of license number thereafter. But most of the works seem to be applicable for a very controlled environment. In the current work, we have concentrated on localization of license plate regions from true color still snapshots captured in a very realistic situation. The technique is based on a novel multi-stage approach for analysis of vertical edge gradients from contrast stretched gray-scale images. The technique successfully localizes the actual license plates in 89.2 % images. Index terms- median filtering, histogram equalization, Sobel’s vertical edge, mean, standard deviation, area, aspect ratio I.