A New Method for Correcting Vehicle License Plate Tilt

Mei-Sen Pan; Qi Xiong; Jun-Biao Yan

doi:10.1007/s11633-009-0210-8

May 2009

Article Contents

Mei-Sen Pan, Qi Xiong and Jun-Biao Yan. A New Method for Correcting Vehicle License Plate Tilt. International Journal of Automation and Computing, vol. 6, no. 2, pp. 210-216, 2009. doi: 10.1007/s11633-009-0210-8

Cite as: Mei-Sen Pan, Qi Xiong and Jun-Biao Yan. A New Method for Correcting Vehicle License Plate Tilt. International Journal of Automation and Computing, vol. 6, no. 2, pp. 210-216, 2009. doi: 10.1007/s11633-009-0210-8

A New Method for Correcting Vehicle License Plate Tilt

1.
Department of Computer Science and Technology, Hunan University of Arts and Science, Changde 415000, PRC;
2.
Office of Academic Affairs, Hunan University of Arts and Science, Changde 415000, PRC

Received: 2008-05-20

Fund Project:

supported by Scientific Research Fund of Hunan Province, PRC (No.07JJ6141);Scientific Research Fund of Hunan Provincial Education Department, PRC (No.06C582)

Abstract

In the course of vehicle license plate (VLP) automatic recognition, tilt correction is a very crucial process. According to Karhunen-Loeve (K-L) transformation, the coordinates of characters in the image are arranged into a two-dimensional covariance matrix, on the basis of which the centered process is carried out. Then, the eigenvector and the rotation angle are computed in turn. The whole image is rotated by -. Thus, image horizontal tilt correction is performed. In the vertical tilt correction process, three correction methods, which are K-L transformation method, the line fitting method based on K -means clustering (LFMBKC), and the line fitting based on least squares (LFMBLS), are put forward to compute the vertical tilt angle . After shear transformation (ST) is imposed on the rotated image, the final correction image is obtained. The experimental results verify that this proposed method can be easily implemented, and can quickly and accurately get the tilt angle. It provides a new effective way for the VLP image tilt correction as well.
- Tilt correction,
- K-L transformation,
- projection profile,
- Hough transformation

References

[1]	T.Naito,T.Tsukada,K.Yamada,K.Kozuka,S.Yamamoto.Robust License-plate Recognition Method for Passing Vehicles under Outside Environment.IEEE Transactions on Vehicular Technology,vol.49,no.6,pp.2309-2319,2000.
[2]	C.N.E.Anagnostopoulos,L E.Anagnostopoulos,V.Loumos,E.Kayafas.A License Plate-recognition Algorithm for Intelligent Transportation System Applications.IEEE Transactions on Intelligent Transportation Systems,vol.7 no.3,pp.377-392,2006.
[3]	R.Zunino,S.Rovetta.Vector Quantization for License Plate Location and Image Coding.IEEE Transactions on Industrial Electronics,vol.47,no.1,pp.159-167,2000.
[4]	P.Comelli,P.Ferragina,M.N.Granieri.Optical Recognition of Motor Vehicle License Plates.IEEE Transactions on Vehicular Technology,vol.44,no.4,pp.790-799,1995.
[5]	S.Kim,D.Kim,Y.Ryu,G.Kim.A Robust License-plate Extraction Method under Complex Image Conditions.In Proceedings of the 16th International Conference on Pattern Recognition,Quebec City,CA,USA,pp.216-219,2002.
[6]	W.J.Li,D.Q.Liang,X.N.Wang,D.Yu.Character Segmentation for Degraded License Plate.Journal of Computer-Aided Design & Computer Graphics,vol.16,no.5,pp.697-700,2004.(in Chinese)
[7]	H.A.Hegt,R.J.Haye,N.A.Khan.A High Performance License Plate Recognition System.In Proceedings of the IEEE International Conference on Systems,Man,and Cybernetics,IEEE Press,vol.5,pp.4357-4362,1998.
[8]	C.Y.Wen,C.C.Yu,Z.D.Hun.A 3D Transformation to Improve the Legibility of License Plate Numbers.Journal of Forensic Sciences,vol.47,no.3,pp.578-585,2002.
[9]	Y.T.Ching.Detecting Line Segments in an Image-A New Implementation for Hough Transform.Pattern Recognition Letters,vol.22,no.3,pp.421-2429,2001.
[10]	L.A.Torres-Mendez,J.C.Ruiz-Suarez,L.E.Sucar,G.Gomez.Translation,Rotation,and Scale-invariant Object Recognition.IEEE,Transactions on Systems,Man,and Cybernetics-Part C,vol.30,no.1,pp.125-130,2000.
[11]	A.Hashizume,P.S.Yeh,A.Rosenfeld.A Method of Detecting the Orientation of Aligned Components.Pattern Recognition Letters,vol.4,no.2,pp.125-132,1986.
[12]	L.O.Gorman.The Document Spectrum for Page Layout Analysis.IEEE Transactions on Pattern Analysis and Machine Intelligence,vol.15,no.11,pp.1162-1173,1993.
[13]	C.Darken,J.Moody,Y.C.Sci,N.Haven.Fast Adaptive Kmeans Clustering:Some Empirical Results.In Proceedings of the International Joint Conference on Neural Networks,vol.2,pp.233-238,1990.
[14]	T.Kanungo,D.M.Mount,N.S.Netanyahu,G.Gomez,C.D.Piatko,R.Silverman,A.Y.Wu.An Efficient K-means Clustering Algorithm:Analysis and Implementation.IEEE Transactions on Pattern Analysis and Machine Intelligence,vol.24,no.7,pp.881-892,2002.
[15]	J.Z.Huang,K.N.Michael,H.Rong,Z.Li.Automated Variable Weighting in K-means Type Clustering.IEEE Transactions on Pattern Analysis and Machine Intelligence,vol.27,no.5,pp.657-668,2005.

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通讯作者: 陈斌, bchen63@163.com

1.
沈阳化工大学材料科学与工程学院沈阳 110142

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A New Method for Correcting Vehicle License Plate Tilt

1. Department of Computer Science and Technology, Hunan University of Arts and Science, Changde 415000, PRC;

2. Office of Academic Affairs, Hunan University of Arts and Science, Changde 415000, PRC

Received: 2008-05-20

Fund Project:

supported by Scientific Research Fund of Hunan Province, PRC (No.07JJ6141);Scientific Research Fund of Hunan Provincial Education Department, PRC (No.06C582)

Key words:

Abstract: In the course of vehicle license plate (VLP) automatic recognition, tilt correction is a very crucial process. According to Karhunen-Loeve (K-L) transformation, the coordinates of characters in the image are arranged into a two-dimensional covariance matrix, on the basis of which the centered process is carried out. Then, the eigenvector and the rotation angle are computed in turn. The whole image is rotated by -. Thus, image horizontal tilt correction is performed. In the vertical tilt correction process, three correction methods, which are K-L transformation method, the line fitting method based on K -means clustering (LFMBKC), and the line fitting based on least squares (LFMBLS), are put forward to compute the vertical tilt angle . After shear transformation (ST) is imposed on the rotated image, the final correction image is obtained. The experimental results verify that this proposed method can be easily implemented, and can quickly and accurately get the tilt angle. It provides a new effective way for the VLP image tilt correction as well.

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Reference (15)

[1]	T.Naito,T.Tsukada,K.Yamada,K.Kozuka,S.Yamamoto.Robust License-plate Recognition Method for Passing Vehicles under Outside Environment.IEEE Transactions on Vehicular Technology,vol.49,no.6,pp.2309-2319,2000.
[2]	C.N.E.Anagnostopoulos,L E.Anagnostopoulos,V.Loumos,E.Kayafas.A License Plate-recognition Algorithm for Intelligent Transportation System Applications.IEEE Transactions on Intelligent Transportation Systems,vol.7 no.3,pp.377-392,2006.
[3]	R.Zunino,S.Rovetta.Vector Quantization for License Plate Location and Image Coding.IEEE Transactions on Industrial Electronics,vol.47,no.1,pp.159-167,2000.
[4]	P.Comelli,P.Ferragina,M.N.Granieri.Optical Recognition of Motor Vehicle License Plates.IEEE Transactions on Vehicular Technology,vol.44,no.4,pp.790-799,1995.
[5]	S.Kim,D.Kim,Y.Ryu,G.Kim.A Robust License-plate Extraction Method under Complex Image Conditions.In Proceedings of the 16th International Conference on Pattern Recognition,Quebec City,CA,USA,pp.216-219,2002.
[6]	W.J.Li,D.Q.Liang,X.N.Wang,D.Yu.Character Segmentation for Degraded License Plate.Journal of Computer-Aided Design & Computer Graphics,vol.16,no.5,pp.697-700,2004.(in Chinese)
[7]	H.A.Hegt,R.J.Haye,N.A.Khan.A High Performance License Plate Recognition System.In Proceedings of the IEEE International Conference on Systems,Man,and Cybernetics,IEEE Press,vol.5,pp.4357-4362,1998.
[8]	C.Y.Wen,C.C.Yu,Z.D.Hun.A 3D Transformation to Improve the Legibility of License Plate Numbers.Journal of Forensic Sciences,vol.47,no.3,pp.578-585,2002.
[9]	Y.T.Ching.Detecting Line Segments in an Image-A New Implementation for Hough Transform.Pattern Recognition Letters,vol.22,no.3,pp.421-2429,2001.
[10]	L.A.Torres-Mendez,J.C.Ruiz-Suarez,L.E.Sucar,G.Gomez.Translation,Rotation,and Scale-invariant Object Recognition.IEEE,Transactions on Systems,Man,and Cybernetics-Part C,vol.30,no.1,pp.125-130,2000.
[11]	A.Hashizume,P.S.Yeh,A.Rosenfeld.A Method of Detecting the Orientation of Aligned Components.Pattern Recognition Letters,vol.4,no.2,pp.125-132,1986.
[12]	L.O.Gorman.The Document Spectrum for Page Layout Analysis.IEEE Transactions on Pattern Analysis and Machine Intelligence,vol.15,no.11,pp.1162-1173,1993.
[13]	C.Darken,J.Moody,Y.C.Sci,N.Haven.Fast Adaptive Kmeans Clustering:Some Empirical Results.In Proceedings of the International Joint Conference on Neural Networks,vol.2,pp.233-238,1990.
[14]	T.Kanungo,D.M.Mount,N.S.Netanyahu,G.Gomez,C.D.Piatko,R.Silverman,A.Y.Wu.An Efficient K-means Clustering Algorithm:Analysis and Implementation.IEEE Transactions on Pattern Analysis and Machine Intelligence,vol.24,no.7,pp.881-892,2002.
[15]	J.Z.Huang,K.N.Michael,H.Rong,Z.Li.Automated Variable Weighting in K-means Type Clustering.IEEE Transactions on Pattern Analysis and Machine Intelligence,vol.27,no.5,pp.657-668,2005.

A New Method for Correcting Vehicle License Plate Tilt

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通讯作者: 陈斌, bchen63@163.com

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