Search

CN-121982693-A - License plate recognition method of electric vehicle

CN121982693ACN 121982693 ACN121982693 ACN 121982693ACN-121982693-A

Abstract

The application discloses a license plate recognition method of an electric vehicle, which relates to the technical field of computer vision and comprises the following steps of obtaining a video image of a target area; detecting the existence of a license plate in a preset area corresponding to the electric vehicle image in the video image under the condition that the electric vehicle exists in the target area according to the video image, acquiring the license plate image under the condition that the existence of the license plate is detected from the preset area of the electric vehicle image, and extracting the acquired license plate image to identify the license plate number. The method is used for accurately positioning the license plate position of the electric vehicle and identifying the license plate number.

Inventors

  • LIN YIPING

Assignees

  • 深圳市小兔新能源科技控股有限公司

Dates

Publication Date
20260505
Application Date
20260403

Claims (10)

  1. 1. The license plate recognition method of the electric vehicle is characterized by comprising the following steps of: acquiring a video image of a target area; detecting the existence of license plates of a preset area corresponding to the electric vehicle image in the video image under the condition that the electric vehicle exists in the target area according to the video image; and under the condition that the existence of the license plate is detected from the preset area of the electric vehicle image, acquiring the license plate image, and extracting the acquired license plate image to identify the license plate number.
  2. 2. The method for identifying a license plate of an electric vehicle as claimed in claim 1, wherein the extracting the acquired license plate image to identify the license plate number comprises: Extracting the acquired license plate image through a rotation target detection algorithm to extract a rotation bounding box corresponding to the license plate image; And acquiring parameters of the rotating bounding box, correcting the acquired license plate image into a horizontal image according to the parameters of the rotating bounding box, and identifying the license plate number.
  3. 3. The method for recognizing the license plate of the electric vehicle according to claim 2, wherein the parameters of the rotating bounding box comprise center coordinates of the license plate image and angles to be rotated, and correcting the acquired license plate image into a horizontal image according to the parameters of the rotating bounding box comprises: And constructing a rotation matrix according to the angle to be rotated by taking the central coordinate of the license plate image as an origin, and executing affine transformation on the acquired license plate image to correct the acquired license plate image into a horizontal image.
  4. 4. The electric vehicle license plate recognition method according to claim 3, wherein the parameters of the rotating bounding box further include a license plate width height, and after the step of correcting the acquired license plate image into a horizontal image according to the parameters of the rotating bounding box is performed, the electric vehicle license plate recognition method further includes: In the corrected horizontal image, a rectangular license plate image is cut out according to the width and height of the license plate by taking the central coordinate of the license plate image as a benchmark; And scaling the cut license plate image to a preset size, and performing binarization or graying treatment.
  5. 5. The electric vehicle license plate recognition method according to claim 2, characterized in that after the step of acquiring the parameters of the rotating bounding box is performed, the electric vehicle license plate recognition method further comprises: The parameters of the normalized rotated bounding box are converted to pixel coordinates at the original image coordinates.
  6. 6. The method for identifying a license plate of an electric vehicle as claimed in claim 2, wherein the identifying a license plate number includes: The method comprises the steps of obtaining a local electric vehicle license plate standard, determining target character characteristics, and recognizing actual characters of a license plate number from a corrected horizontal image through optical character recognition; according to the number and format of the actual characters identified by the target character feature verification, calculating the character confidence; Under the condition that the confidence coefficient of the character is lower than a first preset threshold value, determining whether an electric vehicle exists in the target area or not according to the video image again, or triggering a manual rechecking process; And under the condition that the confidence coefficient of the characters is not lower than a first preset threshold value, directly identifying the license plate number from the horizontal image, or carrying out context correction on the mixed characters in the horizontal image and then identifying the license plate number.
  7. 7. The electric vehicle license plate recognition method according to claim 1, wherein before performing the step of detecting the existence of a license plate of a predetermined area corresponding to an electric vehicle image in a video image in the case where it is determined from the video image that the electric vehicle exists in the target area, the electric vehicle license plate recognition method includes: decoding the acquired video image into a set format, and scaling to a required input resolution; performing adaptive histogram equalization processing for limiting contrast on an image brightness channel in the presence of uneven illumination; Carrying out normalization processing on pixel values of the video image, and carrying out standardization processing according to a set mean value and a standard deviation; It is determined whether an electric vehicle is present in a target area of the processed video image.
  8. 8. The method for identifying a license plate of an electric vehicle as recited in claim 7, wherein determining whether the electric vehicle is present in the target area of the processed video image comprises: Determining whether a moving target exists in a target area of the processed video image through frame differential motion detection; acquiring the detection confidence of the processed video image under the condition that a moving target exists; Under the condition that the detection confidence is not lower than a second preset threshold value, determining that an electric vehicle exists in a target area of the processed video image; Before the step of detecting the existence of the license plate of the preset area corresponding to the electric vehicle image in the video image is executed under the condition that the electric vehicle exists in the target area according to the video image, the method further comprises the following steps: extracting a corresponding electric vehicle detection frame from a target area of the processed video image; performing redundancy elimination treatment on the extracted electric vehicle detection frame through non-maximum value inhibition, and performing size filtering treatment on the extracted electric vehicle detection frame according to the target size; and extracting the electric vehicle image from the target area of the video image based on the processing result.
  9. 9. The method for identifying a license plate of an electric vehicle as recited in claim 7, wherein determining whether the electric vehicle is present in the target area of the processed video image comprises: Determining whether a moving target exists in a target area of the processed video image through frame differential motion detection; acquiring the detection confidence of the processed video image under the condition that a moving target exists; Under the condition that the detection confidence is not lower than a second preset threshold value, determining that an electric vehicle exists in a target area of the processed video image; before the step of detecting the existence of license plates in the predetermined area corresponding to the electric vehicle image in the video image is executed when the electric vehicles exist in the target area and the number of the electric vehicles is determined to be a plurality of according to the video image, the method further comprises: extracting a corresponding electric vehicle detection frame from a target area of the processed video image; And calculating and screening out an electric vehicle detection frame with the largest pixel area relative to the video image, and extracting images of a plurality of electric vehicles from the screened electric vehicle detection frame.
  10. 10. The electric vehicle license plate recognition method according to any one of claims 1 to 9, characterized in that the electric vehicle license plate recognition method further comprises the steps of: Under the condition that no license plate exists in a preset area of an electric vehicle image, packaging a license plate-free alarm event and reporting the license plate-free alarm event to a back-end management system so as to trigger a license plate-free alarm mode; After the step of identifying the license plate number is executed, the method for identifying the license plate of the electric vehicle further comprises the following steps: and transmitting the identified license plate number to a back-end management system to trigger a passing control mode.

Description

License plate recognition method of electric vehicle Technical Field The application relates to the technical field of computer vision, in particular to a license plate recognition method of an electric vehicle. Background With the acceleration of the urban process, the electric vehicle has become one of the main vehicles for short-distance travel of residents. Meanwhile, the safety management problem of the electric vehicle is increasingly outstanding, the problem is mainly solved that no-license and fake-license electric vehicles are on a large scale to bring serious difficulties to traffic law enforcement and accident tracing, the fact that the entrance and exit of places such as residential communities and commercial buildings lack of effective license plate verification means of the electric vehicles leads to outstanding potential safety hazards, the efficiency of the traditional manual verification mode is low, and the requirement of high-flow traffic management in peak hours is difficult to meet. In the related art, an object detection method based on an axis alignment rectangular frame is mainly adopted for automatic detection of the license plate, but the method has lower positioning accuracy on the license plate, so that the license plate number cannot be accurately identified later. Based on the above, how to provide a method capable of accurately positioning the license plate position and identifying the license plate number of the electric vehicle becomes a technical problem to be solved. Disclosure of Invention The application mainly aims to provide a license plate recognition method of an electric vehicle, which aims to solve the technical problem of how to accurately position the license plate of the electric vehicle and recognize the license plate number. In one aspect, a license plate recognition method of an electric vehicle is provided, which includes the following steps: acquiring a video image of a target area; detecting the existence of license plates of a preset area corresponding to the electric vehicle image in the video image under the condition that the electric vehicle exists in the target area according to the video image; and under the condition that the existence of the license plate is detected from the preset area of the electric vehicle image, acquiring the license plate image, and extracting the acquired license plate image to identify the license plate number. In an embodiment, the extracting the acquired license plate image to identify the license plate number includes: Extracting the acquired license plate image through a rotation target detection algorithm to extract a rotation bounding box corresponding to the license plate image; And acquiring parameters of the rotating bounding box, correcting the acquired license plate image into a horizontal image according to the parameters of the rotating bounding box, and identifying the license plate number. In an embodiment, the parameters of the rotation bounding box include a license plate image center coordinate and an angle to be rotated, and the correcting the acquired license plate image into a horizontal image according to the parameters of the rotation bounding box includes: And constructing a rotation matrix according to the angle to be rotated by taking the central coordinate of the license plate image as an origin, and executing affine transformation on the acquired license plate image to correct the acquired license plate image into a horizontal image. In an embodiment, the parameters of the rotating bounding box further include license plate width and height, and after the step of correcting the acquired license plate image into the horizontal image according to the parameters of the rotating bounding box is performed, the method for identifying the license plate of the electric vehicle further includes: In the corrected horizontal image, a rectangular license plate image is cut out according to the width and height of the license plate by taking the central coordinate of the license plate image as a benchmark; And scaling the cut license plate image to a preset size, and performing binarization or graying treatment. In an embodiment, after the step of obtaining the parameter of the rotating bounding box is performed, the license plate recognition method of the electric vehicle further includes: The parameters of the normalized rotated bounding box are converted to pixel coordinates at the original image coordinates. In one embodiment, the identifying the license plate number includes: The method comprises the steps of obtaining a local electric vehicle license plate standard, determining target character characteristics, and recognizing actual characters of a license plate number from a corrected horizontal image through optical character recognition; according to the number and format of the actual characters identified by the target character feature verification, calculating the character confidence; Under t