Vehicle license plate image vertical tilt correction method

A technology of vertical tilt and license plate image, which is applied in the direction of instruments, character and pattern recognition, computer parts, etc., can solve the problems of large amount of calculation and low accuracy, and achieve the effect of simplifying calculation, satisfying real-time performance and improving calculation efficiency

Inactive Publication Date: 2014-11-19
UNIV OF ELECTRONIC SCI & TECH OF CHINA
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The purpose of the present invention is to provide a method for correcting the vertical inclination of license plate images based on envelope correlation. The existing license plate image vertical tilt correction method has the problems of large amount of calculation and low accuracy

Method used

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  • Vehicle license plate image vertical tilt correction method
  • Vehicle license plate image vertical tilt correction method
  • Vehicle license plate image vertical tilt correction method

Examples

Experimental program
Comparison scheme
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Embodiment 1

[0032] Embodiment 1: Taking an artificially set license plate image with a vertical tilt angle as an example:

[0033] In this embodiment, seven characters are randomly selected from the possible value collection of license plate characters, and a license plate image with a vertical inclination angle of 20 degrees to the positive direction of the x-axis is constructed, and the size of the license plate image is 120×566 (pixels). For example, select the license plate character as: {Beijing AF0236}, such as Figure 5 shown. Among them, the value set of the non-Chinese character part of the license plate character is a combination of numbers {0-9} and English letters {A-Z}. "Learning", "Jing" and other special Chinese characters.

[0034] The specific implementation process of this embodiment is as follows:

[0035] Step 101: record the height and width of the license plate binary image as H=120 (pixel) and W=566 (pixel) respectively, ask for the upper package of the license p...

Embodiment 2

[0051] Embodiment 2: Taking the license plate image with a vertical tilt angle for actual shooting as an example:

[0052] The image in this embodiment is the license plate image actually taken. During the actual shooting process, if the camera is not directly in front of the license plate, the captured image will have a certain degree of vertical inclination. First locate the license plate to the captured image, then carry out binarization processing and horizontal tilt correction to the license plate, remove the upper and lower borders of the license plate image at last, and obtain the license plate image as the input image of this embodiment, and the image size is 140 × 620 (pixels) .

[0053] The specific implementation process of this embodiment is as follows:

[0054] Step 101: the height and the width of the license plate binary image of note input are H=140 (pixel) and W=620 (pixel) respectively, seek the license plate binary image of input (horizontal inclination cor...

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Abstract

The invention belongs to the technical field of vehicle license plate recognition and correction and discloses a vehicle license plate image vertical tilt correction method for determining a vertical tile angle based on cross correlation. According to the method, based on the principles of envelope and cross correlation, the vertical tile angle of a vehicle license plate binary image is determined through calculating the ratio of an offset of a horizontal coordinate corresponding to the cross correlation maximum value of upper envelope and lower envelope on a vehicle license plate binary image, and the vertical tile of the vehicle license plate binary image is corrected through shear transformation. According to the method, an iterative solution way is employed, a vertical tilt angle error caused the asymmetry of the upper envelope and lower envelope is overcome, the vehicle license plate image vertical tilt correction method has the advantages of fast operation speed and high accuracy, and the real-time requirement by a vehicle license plate recognition system is fully satisfied.

Description

technical field [0001] The invention belongs to the technical field of license plate recognition and correction, in particular to a method for correcting the vertical inclination of a license plate image based on envelope correlation. Background technique [0002] License plate recognition is an important part of intelligent transportation system. License plate recognition technology refers to a technology that uses a processing system to perform a series of processing on the license plate image, extract characters from the input image and recognize the license plate characters. The license plate recognition process can be divided into six parts: license plate image acquisition, license plate image enhancement, license plate location, license plate tilt correction, license plate character segmentation, and license plate character recognition. The tilt correction of the license plate is an important image processing process before the character segmentation of the license pl...

Claims

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Application Information

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IPC IPC(8): G06K9/32
Inventor 李晓峰傅志中徐进周宁赵宇
Owner UNIV OF ELECTRONIC SCI & TECH OF CHINA
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