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A new method for correcting vehicle license plate tilt

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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 α are computed in turn. The whole image is rotated by −α. 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 σ. 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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Authors and Affiliations

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

    Mei-Sen Pan & Qi Xiong

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

    Qi Xiong & Jun-Biao Yan

Authors
  1. Mei-Sen Pan
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  2. Qi Xiong
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  3. Jun-Biao Yan
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Corresponding author

Correspondence to Mei-Sen Pan.

Additional information

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

Mei-Sen Pan graduated from Hunan Normal University, PRC, in 1995. He received the M. Sc. degree from Huazhong University of Science and Technology, PRC, in 2005. He is currently an associate professor in Hunan University of Arts and Science, PRC.

His research interests include vehicle license plate image processing, information fusion, artificial neural network, and software engineering.

Qi Xiong graduated from Changde College, PRC, in 1993. He received the M. Sc. degree from Huazhong University of Science and Technology, PRC, in 2005. He is currently a senior engineer in Hunan University of Arts and Science, PRC.

His research interests include digital image processing, embed system, and software engineering.

Jun-Biao Yan graduated from Donghua University, PRC, in 1983. He received the M. Sc. degree from College of Computer Science and Technology, Huazhong University of Science and Technology, PRC, in 2005. He is currently an associate professor in Hunan University of Arts and Science, PRC.

His research interests include digital image processing, electronic commerce, and software engineering.

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Pan, MS., Xiong, Q. & Yan, JB. A new method for correcting vehicle license plate tilt. Int. J. Autom. Comput. 6, 210–216 (2009). https://doi.org/10.1007/s11633-009-0210-8

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  • DOI: https://doi.org/10.1007/s11633-009-0210-8

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