Information Card Detection via Perspective Correction and Gradient Matching
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Solution Overview
Problem
Current methods for detecting information cards in images, such as identity cards, social security cards, and driving licenses, require high user cooperation and are slow due to the need for precise template matching, which is inefficient and prone to errors.
Innovation Solution
A method involving line detection to find the endpoints of the card's sides, generating linear equations, calculating intersection points, and performing perspective transformation to create a gradient template for matching, reducing user interaction and improving processing speed by automatically correcting image deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If template matching method is used to detect identity card, then detection accuracy can be maintained, but processing speed deteriorates and user cooperation requirement increases
Solution Approach 1:
The patent segments the detection process into distinct phases: first performing line detection to identify card boundaries, then applying perspective transformation to correct deformation, and finally performing template matching on the corrected image. This segmentation allows each step to focus on a specific task, improving overall efficiency while maintaining accuracy.
Solution Approach 2:
The patent performs preliminary perspective transformation and image correction before template matching. By pre-processing the image to correct deformation and align it with the template, the subsequent template matching operates on an optimized image, significantly reducing processing time and improving detection speed without sacrificing accuracy.
2Measurement precision
If template matching method is used to detect identity card, then detection accuracy can be maintained, but user cooperation requirement increases
Solution Approach 1:
The system performs automatic perspective transformation and image correction without requiring user intervention. The algorithm automatically detects line segments, calculates perspective transformation matrices, and corrects image deformation, making the system self-sufficient and eliminating the need for users to manually adjust image parameters.
Solution Approach 2:
By performing preliminary perspective transformation and alignment automatically, the system prepares the image for template matching without user input. This preliminary automatic processing ensures that the template matching can proceed with high accuracy while requiring minimal user cooperation.
3Reliability
If full image scanning is performed for template matching, then detection completeness is improved, but processing time increases
Solution Approach 1:
The patent extracts the region of interest by first performing line detection to identify card boundaries and then applying perspective transformation to isolate the card area. By extracting and focusing only on the relevant card region rather than scanning the entire image, the system maintains detection completeness while significantly reducing processing time.
Solution Approach 2:
The detection process is segmented into boundary detection, perspective transformation, and template matching phases. This segmentation allows the system to process only the relevant card region in the final template matching stage, improving efficiency while maintaining completeness through the preliminary boundary detection and correction steps.
Data Source
AI summary
A method for detecting an information card in an image is provided. The method includes performing a line detection to obtain two endpoints of a line segment corresponding to each of four sides of the information card; generating, a linear equation of the side; obtaining coordinates of four intersection points of the four sides of the information card; mapping the coordinates of the four intersection points to four corners of a rectangular box of the information card, to obtain a perspective transformation matrix; performing perspective transformation on image content encircled by four straight lines represented by the four linear equations to provide transformed image content; forming a gradient template according to a layout of information content on the information card; and using the gradient template to match with the transformed image content and determining whether the image content is a correct information card.