Variance Window Based Car License Plate Localization

Jing Pang

Department of Electrical & Electronic Engineering, Computer Engineering Program, California State University, Sacramento, CA, USA.

DOI: 10.4236/jcc.2014.29009                

Abstract

In this paper, a new method for discovering the candidate car license plate locations is presented. First, the image is decomposed using a Haar wavelet to get the HL band with vertical edges. Then, the HL band image is binarized using an Otsu threshold. Next a black top-hat algorithm is applied to reduce the effects of interfering large continuous features other than the license plate. At this time, a moving window based modified variance score calculation is made for areas with white pixels. This work found that the top 3 detected rectangle windows correctly locate the license plate regions with a success rate of about 98.2%. Moreover, the proposed method is robust enough to locate the plates in cases where the rough vehicle position has not been previously discovered and the cars are not centered in the image.

Keywords

Harr Wavelet, Black Top-Hat, Binarization, Moving Window, Variance Score

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Xu, J.F., Li, S.F. and Yu, M.S. (2004) Car License Plate Extraction Using Color and Edge Information. Proceedings of International Conference on Machine Learning and Cybernetics, Shanghai, 26-29 August 2004, 3904-3907. http://dx.doi.org/10.1109/ICMLC.2004.1380528
[2]	Ahmadyfard, A. and Abolghasemi, V. (2008) Detecting License Plate Using Texture and Color Information. International Symposium on Telecommunications, Tehran, 27-28 August 2008, 804-808. http://dx.doi.org/10.1109/ISTEL.2008.4651410
[3]	Yang, Q.W., Yang, C.H., Li, C.H. and Wang, H.Z. (2011) Research on License Plate Detection Based on Salient Feature under Complex Background. 1 Sixth International Conference on Image and Graphics, Hefei, 12-15 August 2011, 609-615. http://dx.doi.org/10.1109/ICIG.2011.59
[4]	Wang, R., Wang, G.Y. and Wang, Z.H. (2012) A Fast Method for Two-Stage Precise License Plate Location Based on Fusion of Corner Feature and Gray Level Jumps. International Conference on Industrial Control and Electronics Engineering, Xi’an, 23-25 August 12, 976-979. http://dx.doi.org/10.1109/ICICEE.2012.259
[5]	Ghazal, M. and Hajjdiab, H. (2013) License Plate Automatic Detection and Recognition Using Level Sets and Neural Networks. 1st International Conference on Communications, Signal Processing, and Their Applications, Sharjah, 12- 14 February 2013, 1-5. http://dx.doi.org/10.1109/ICCSPA.2013.6487280
[6]	Becerikli, Y., Olgac, A.V., Sen, E. and Coskun, F. (2007) Neural Network Based License Plate Recognition System. International Joint Conference on Neural Networks, Florida, 12-17 August 2007, 3057-3061. http://dx.doi.org/10.1109/IJCNN.2007.4371448
[7]	Xia, H.D. and Liao, D.C. (2011) The Study of License Plate Character Segmentation Algorithm Based on Vertical Projection. International Conference on Consumer Electronics, Communications and Networks, Xianning, 16-18 April 2011, 4583-4586. http://dx.doi.org/10.1109/CECNET.2011.5768714
[8]	Jagannathan, J., Sherajdheen, A., Deepak, R.M.V. and Krishnan, N. (2013) License Plate Character Segmentation Using Horizontal and Vertical Projection with Dynamic Thresholding. International Conference on Emerging Trends in Computing, Communication and Nanotechnology, Tirunelveli, 25-26 March 2013, 700-705. http://dx.doi.org/10.1109/ICE-CCN.2013.6528594
[9]	Franc, V. and Hlavác, V. (2005) License Plate Character Segmentation Using Hidden Markov Chains. Proceedings of 27th DAGM Conference on Pattern Recognition, Vienna, 30 August-2 September 2005, 385-392. http://dx.doi.org/10.1007/11550518_48
[10]	Lin, B., Fang, B. and Li, D.H. (2009) Character Recognition of License Plate Image Based on Multiple Classifiers. International Conference on Wavelet Analysis and Pattern Recognition, Baoding, 12-15 July 2009, 138-143. http://dx.doi.org/10.1109/ICWAPR.2009.5207413
[11]	Zeng, Y.C. and Chen, J.F. (2010) Adaptive Template-Matching Method for Recognition of Low-Resolution License Number. International Computer Symposium, Tainan, 16-18 December 2010, 228-233. http://dx.doi.org/10.1109/COMPSYM.2010.5685512
[12]	Miao, L.G. (2012) License Plate Character Segmentation Algorithm Based on Variable-Length Template Matching. IEEE 11th International Conference on Signal Processing, Beijing, 21-25 October 2012, 947-951. http://dx.doi.org/10.1109/ICoSP.2012.6491736
[13]	Wazalwar, D., Oruklu, E. and Saniie, J. (2012) A Design Flow for Robust License Plate Localization and Recognition in Complex Scenes. Journal of Transportation Technologies, 2, 13-21. http://dx.doi.org/10.4236/jtts.2012.21002
[14]	Zhang, H.F., Jia, W.J., He, X.J. and Wu, Q. (2006) Learn-ing-Based License Plate Detection Using Global and Local Features. 18th International Conference on Pattern Recognition, Vol. 2, Hong Kong, 1102-1105. http://dx.doi.org/10.1109/ICPR.2006.758
[15]	Kim, K.K., Kim, K.I., Kim, J.B. and Kim, H.J. (2000) Learning-Based Approach for License Plate Recognition. Proceedings of the IEEE Signal Processing Society Workshop: Neural Networking for Signal Processing X, Sydney, 11-13 December 2000, 614-623. http://dx.doi.org/10.1109/NNSP.2000.890140
[16]	Suryanarayana, P.V., Mitra, S.K., Banerje, A. and Roy, A.K. (2005) A Morphology Based Approach for Car License Plate Extraction. Annual IEEE INDICON, 11-13 December 2005, 24-27. http://dx.doi.org/10.1109/INDCON.2005.1590116
[17]	Ye, Y.Y., Chen, W.M., Hu, J.D. and Zou, W.B. (2010) Research on Localization Method of Vehicle License Plate Based on Wavelet Analysis. 2nd International Conference on Networking and Digital Society, Wenzhou, 30-31 May 2010, 672-675. http://dx.doi.org/10.1109/ICNDS.2010.5479394
[18]	Wu, M.K., Wei, J.S., Shih, H.C. and Ho, C.C. (2009) 2-Level-Wavelet-Based License Plate Edge Detection. Fifth International Conference on Information Assurance and Security, Xi’an, 18-20 August 2009, 385-388. http://dx.doi.org/10.1109/IAS.2009.295
[19]	Li, X.P., Lv, X.X., Wang, S.Z., Zhang, L., Li, Y.X. and Dong, H.J. (2010) Research on the Recognition Algorithm of the License Plate Character Based on the Multi-resolution Template Matching. 4th International Conference on New Trends in Information Science and Service Science, Gyeongju, 11-13 May 2010, 341-344.
[20]	Dlagnekov, L. and Belongie, S. UCSD/Calit2 Car License Plate, Make and Model Database. http://vision.ucsd.edu/car_data.html
[21]	Hsieh, C.T. and Juan, Y.S. (2005) Wavelet Transform Based License Plate detection for Cluttered Scene. WSEAS Transactions on Computers, 4, 30-33.
[22]	Wu, M.K., Wei, J.S., Shih, H.C. and Ho, C.C. (2009) License Plate Detection Based on 2-Level 2D Haar Wavelet Transform and Edge Density Verification. IEEE International Symposium on Industrial Electronics, Seoul, 5-8 July 2009, 1699-1704. http://dx.doi.org/10.1109/ISIE.2009.5214275