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Method for correcting certificate image inclination

A tilt correction, image technology, applied in image analysis, image data processing, graphic image conversion and other directions, can solve problems such as large amount of calculation and easy to miss detection

Inactive Publication Date: 2010-01-13
谭洪舟
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  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

However, the direct Hough transform has the disadvantages of large amount of calculation, prone to missed detection and other accuracy rates.

Method used

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  • Method for correcting certificate image inclination
  • Method for correcting certificate image inclination
  • Method for correcting certificate image inclination

Examples

Experimental program
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specific Embodiment

[0103] Use a USB network camera with a resolution of 640×480 to take a horizontally placed image of a second-generation resident ID card, and rotate the image of the ID card obtained by it by 13 degrees clockwise (this operation is to test the method of the present invention Whether the detected tilt angle is equal to the theoretical rotation angle).

[0104] From the image of the certificate, it can be judged that the ratio of the certificate to the entire image is still relatively large, so the reduction factor of the above image is 1 / 4 zoom operation, such as Figure 4 shown;

[0105] Perform color space transformation on the reduced image, use YCbCr color difference to describe, and take out the brightness component, such as Figure 5 shown;

[0106] Use the Sobel gradient operator for edge detection to obtain rough document image contour information, such as Figure 6 shown;

[0107] Use the thinning algorithm to Figure 6 Thinning operation is performed, and the obt...

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Abstract

The invention discloses a method for calculating angle of inclination and correcting inclination by using image contour information and combing Hough conversion. The method comprises: a) using an image collection device to obtain a certificate image; b) reducing the obtained certificate image; c) carrying out grey treatment on the certificate image; d) using an Sobel operator module to detect the edges of the gray image to obtain a thicker wide profile image; e) carrying out detailing operation on the treated image to obtain a profile image with thin edges and one pixel width; f) carrying out Hough conversion on the obtained profile image with thin edges to detect the line parameter of a frame, and using detected parameter to calculate to obtain the angle of inclination of an original certificate; and g) using the obtained angle of inclination to rotate the image. The invention fully utilizes reduced image contour information and uses Hough conversion to calculate the angle of inclination, which greatly reduces points participating in operation, improves algorithm efficiency and ensures high accuracy, strong robustness and high reliability of algorithm detection.

Description

technical field [0001] The invention discloses a method for correcting the inclination of a certificate image, specifically, it designs a method for calculating the inclination angle by using image contour information combined with Hough transformation, which belongs to the technical field of digital image processing. Background technique [0002] In many fields of social and people's livelihood, it is often necessary to obtain relevant information from certificates. With the maturity of computer technology, image processing and optical character recognition technology, it has become possible to use computer to automatically identify and enter document information, which can greatly improve the efficiency of both parties. The document information collection system based on computer OCR can be widely used in Internet cafes, public security, banking, telecommunications, postal services, hotels, railways, civil aviation, securities, civil affairs, education, entry-exit, militar...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06T7/00G06T3/40
Inventor 谭洪舟朱雄泳文旭华
Owner 谭洪舟
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