Color license plate positioning method

A license plate positioning and color technology, applied in the direction of instruments, character and pattern recognition, computer components, etc., can solve the problems that the license plate color is easily affected by changes in lighting conditions, and there are many false detections and missed detections

Inactive Publication Date: 2011-05-25
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This type of method is simple to implement, fast in processing speed, insensitive to changes in lighting conditions, and has good positioning performance for license plate tilt and deformation. The disadvantage is that there are many false detections.
This kind of method comprehensively considers the color and edge features of the license plate, which can reduce fals...

Method used

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  • Color license plate positioning method
  • Color license plate positioning method
  • Color license plate positioning method

Examples

Experimental program
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Embodiment Construction

[0035]The embodiment of the present invention adopts VC++2005 under Windows XP SP3 system as the emulation platform. The car images used in the experiment are real-shot car images from highway toll stations provided by the cooperative unit, a total of 385 images, including 418 complete license plates. Among them, there are 286 daytime images, 132 nighttime images, 284 blue license plates, and 134 yellow license plates. The image resolution of the surveillance camera is 1024×768pixels.

[0036] The technical scheme of the invention mainly includes three parts: color space conversion, initial positioning of the license plate area and precise positioning of the license plate area. The specific plan is as follows:

[0037] 1. Color space conversion

[0038] The color car image captured by the camera is usually stored in JPEG format, and the color space used is usually sRGB (standard Red Green Blue). Use the standard given by CIELab1976 to complete the transformation from sRGB ...

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Abstract

The invention belongs to the field of automatic license plate recognition and application of intelligent video monitoring, and relates to a color license plate positioning method. The method comprises the following steps of: acquiring CIELab color space automobile images; normalizing the images; performing morphological expansion processing on four classes of binary images by using diamond structure elements; obtaining a blue-white edge binary image, and obtaining a yellow-black edge binary image; performing expansion processing on the two edge binary images by using horizontal strip structure elements, and marking each potential license plate region; and setting four constraint conditions, namely constraint of license plate region area, relative size constraint of width and height of a license plate and width and height of an image, width-to-height ratio constraint of the license plate and shape constraint of the license plate, recognizing each potential license plate region and extracting the license plate region. The invention has the advantages that: the method is low in calculation quantity and high in processing speed, and is not affected by the interference region and the illumination condition change.

Description

Technical field [0001] The invention belongs to the application field of automatic license plate recognition of intelligent video monitoring, and in particular relates to a license plate positioning method directly aimed at color images. Background technique [0002] Vehicle License Plate Recognition (LPR for short) technology is an important part of the intelligent transportation system. It is widely used in video surveillance fields such as unmanned parking lot, non-parking toll collection and traffic flow control. The LPR system based on computer vision is mainly composed of three parts [1]: license plate location, license plate character segmentation and character recognition. Among them, the license plate location is a key issue of the LPR system, which realizes the judgment of the position of the license plate area in the image. [0003] Domestic research on license plate positioning began in the 1990s and has roughly experienced three stages of development. Early r...

Claims

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Application Information

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IPC IPC(8): G06K9/00
Inventor 王建刘立王天慧
Owner TIANJIN UNIV
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