Local enhancement of car image for license plate detection

In this paper we address the problem of car plate detection. In the first part of algorithm we propose a method for enhancing car plate regions. We estimate the local density of vertical edges in the image as a criterion for local enhancement. In the second part, the vertical edges from the enhanced image is then extracted and feed to a morphological filter to constitute candidate regions for the place of car plate. This filter aims to connect vertical edges closer than the size of a defined structuring element. The output of this process is a number of connected components among which the plate region is. We use some geometrical features of car plate such as shape and aspect ratio to filter out non-plate regions from the candidate list. Using the correlation between the candidate regions and the model of car plate, the most probable region is found. The result of enhancement on car images shows the ability of the proposed method for improving the contrast of plate region(s) in the image. The experimental results on out-door car images confirms the robustness of the proposed method against the severe imaging condition.

[1]  Changping Liu,et al.  A hybrid License Plate Extraction Method Based On Edge Statistics and Morphology , 2004, ICPR.

[2]  Ioannis Anagnostopoulos,et al.  A License Plate-Recognition Algorithm for Intelligent Transportation System Applications , 2006, IEEE Transactions on Intelligent Transportation Systems.

[3]  Nelson H. C. Yung,et al.  Recognition of vehicle registration mark on moving vehicles in an outdoor environment , 1999, Proceedings 199 IEEE/IEEJ/JSAI International Conference on Intelligent Transportation Systems (Cat. No.99TH8383).

[4]  Kosin Chamnongthai,et al.  The recognition of car license plate for automatic parking system , 1999, ISSPA '99. Proceedings of the Fifth International Symposium on Signal Processing and its Applications (IEEE Cat. No.99EX359).

[5]  Jiaxin Wang,et al.  An efficient method of license plate location , 2005, Pattern Recognit. Lett..

[6]  Sunil Kumar,et al.  Locating text in images using matched wavelets , 2005, Eighth International Conference on Document Analysis and Recognition (ICDAR'05).

[7]  S Draghici,et al.  A NEURAL NETWORK BASED ARTIFICIAL VISION SYSTEM FOR LICENSE PLATE RECOGNITION , 1997 .

[8]  Muhittin Gökmen,et al.  License Plate Character Segmentation Based on the Gabor Transform and Vector Quantization , 2003, ISCIS.

[9]  Sei-Wang Chen,et al.  Automatic license plate recognition , 2004, IEEE Transactions on Intelligent Transportation Systems.

[10]  Shohreh Kasaei,et al.  An Efficient Features - Based License Plate Localization Method , 2006, 18th International Conference on Pattern Recognition (ICPR'06).

[11]  Fernando Martín,et al.  NEW METHODS FOR AUTOMATIC READING OF VLP's (VEHICLE LICENSE PLATES) , 2002 .

[12]  Weizhong Zhao,et al.  Automatic License Plate Recognition System Based on Color Image Processing , 2005, ICCSA.

[13]  E.D. Di Claudio,et al.  Car plate recognition by neural networks and image processing , 1998, ISCAS '98. Proceedings of the 1998 IEEE International Symposium on Circuits and Systems (Cat. No.98CH36187).

[14]  Lambert Spaanenburg,et al.  Car license plate recognition with neural networks and fuzzy logic , 1995, Proceedings of ICNN'95 - International Conference on Neural Networks.

[15]  Sorin Draghici,et al.  A Neural Network Based Artificial Vision System for Licence Plate Recognition , 1997, Int. J. Neural Syst..