Method for automatic extraction of license plate position in vehicle monitoring image and perspective correction

Abstract

The invention discloses a method for the automatic extraction of the position of a license plate in a vehicle monitoring image and perspective correction, and the method comprises the steps: finding an approximate range of the license plate in the image through employing the edge and color information; carrying out the linear detection of the image; determining four boundary lines forming a perspective deformation license plate through employing the regional boundary information and combining with significant straight lines; solving four intersection points of the significant straight lines, and building mapping relation between the four intersection points with four corners of a target rectangle; carrying out the reverse calculation of a perspective correction matrix, and completing the perspective correction of a license plate. The method obtains the positions of four corners of a license plate with perspective distortion, builds the mapping relation between the four corners of the license plate with perspective distortion and the four corners of the target rectangle, calculates a perspective transformation matrix, and completes the perspective correction of the license plate. Compared with an affine transformation method based on horizontal and vertical rotation, the method truly describes the perspective transformation, and guarantees the higher license plate image correction precision. Compared with an affine transformation algorithm, the method can detect the perspective distortion information of the license plate, also can precisely locate the boundary corners of the license plate, calculates the perspective transformation matrix, and accurately achieves the perspective correction of the license plate.

Description

technical field [0001] The invention belongs to the field of computer application technology, and in particular relates to a method for automatically extracting the position of a license plate in a vehicle monitoring image and performing perspective correction. Background technique [0002] At present, automatic license plate recognition technology is a research hotspot in the field of computer vision, and it is also an important part of urban and traffic intelligent systems. The automatic license plate recognition technology generally goes through three basic operations of license plate extraction, character segmentation and character recognition. Affected by factors such as weather, light, and shadows, the accuracy of license plate recognition algorithms often fluctuates and even fails to recognize or recognize errors. Locating the license plate with high precision in a complex environment is the key link for the license plate recognition system to improve the recognition...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a method for automatically extracting the position of the license plate in the vehicle monitoring image and correcting it in perspective, aiming at solving the problems of low accuracy and poor robustness in the license plate positioning and correction in the existing license plate recognition method

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