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Research and Modification of License Plate Tilt Correction Algorithms

CHEN Ling1, 3，4, LI Xi-ying2,3,4, LU Lin2,3,4   

  1. 1. School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China；
    2. School of Engineering, Sun Yat-sen University, Guangzhou 510275, China
    3. Guangdong Provincial Key Laboratory of Intelligent Transportation System, Guangzhou 510275, China;
    4. Key Laboratory of Video and Image Intelligent Analysis and Application Technology of Ministry of Public Security, P. R. China, Guangzhou 510275, China
  • Received:2013-06-27 Revised:1900-01-01 Online:2013-12-18 Published:2013-12-18

Abstract: License plate tilt correction is a necessary step before characters segment, which has a direct effect on segmentation. License plate tilt combines with rotary in horizontal direction and shear in vertical direction. By studying the existing main tilt correction algorithms: Hough transformation method, rotating projection method, characteristic line method, orientation image method, some of improved algorithms is presented. Experiments prove that those improved methods are more effective. Another experiment indicates that rotating projection method is more successful than fitting line method in shear correction.

Key words: license plate tilt, tilt correction, Hough transform, Radon transform, characteristic line, orientation image