Towards an automatic vehicle access control system: License plate location

• Published in: 2011 IEEE International Conference on Systems, Man, and Cybernetics pp. 2916 - 2921
• Main Authors: Mendes, P.R., Neves, J.M.R., Tavares, A.I., Menotti, D.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01-10-2011
• Subjects: Access control; Filtering; Image databases; Licenses; mathematical morphology; Morphological operations; Vehicle license plate location; Vehicles
• ISBN: 9781457706523; 1457706520
• ISSN: 1062-922X; 2577-1655
• DOI: 10.1109/ICSMC.2011.6084108

An automatic vehicle access control system (AVACS) can be divided into three steps: vehicle location, vehicle license plate (VLP) location, and VLP recognition. This paper presents a new method for VLP location based on the horizontal gradient, morphological operations, connected components analysis, and statistical measures. First, the horizontal gradient is acquired and a mean filter is applied on it. Morphological operations are then used to darken non-VLP high-valued regions (saliences). At this step, we work on an integer-valued image rather than on the binary one, improving salience detection. Finally, the image is binarized, then a connected component analysis is performed, and statistical measures are used to decide among the VLP candidates. Experiments show that, in a database of 722 images, our method correctly locates the VLP in 95% of the cases, outperforming previous approaches.