Image Distortion Correction Using Virtual Line Segments

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Solution Overview

Problem

Existing image processing devices struggle to correct distortion in captured images when the subject is not fully contained within the frame or is not a document, requiring manual adjustment or detection of line segments, which can be impractical for non-document subjects like whiteboards or guide maps.

Innovation Solution

An image processing device that generates a line segment image by extracting contour line segments, identifies a quadrilateral using virtual and contour line segments, and corrects distortion in perspective transformation based on this quadrilateral, allowing for automatic correction without manual adjustment and accommodating non-document subjects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If manual adjustment is used to correct distortion degree, then correction flexibility is improved, but operation complexity increases and automation decreases

Engineering Contradiction:

Improvemanual adjustment flexibilityVSAvoidautomatic correction

Core Design Contradiction:

Ease of operationVSExtent of automation

Solution Approach 1:

The system automatically detects line segments in the captured image and computes the distortion correction parameters without requiring manual user input. The processor identifies contour line segments, determines the quadrilateral shape, and calculates the correction transformation autonomously, making the system self-sufficient in the correction process.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces manual mechanical adjustment operations with automated image processing algorithms. Instead of requiring users to manually adjust correction parameters, the system uses computer vision techniques to detect line segments and automatically computes the distortion correction, substituting human operation with computational processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If the subject must be wholly contained in the imaging area to correct distortion, then detection accuracy is improved, but adaptability decreases

Engineering Contradiction:

Improvedistortion detection accuracyVSAvoidsubject coverage range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The system does not require the complete quadrilateral subject to be visible in the captured image. Instead, it suffices to detect at least two line segments that can define the distortion characteristics. This partial action approach allows correction even when parts of the subject extend beyond the imaging area, enhancing adaptability while maintaining sufficient accuracy for correction purposes.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If line segment detection is required for distortion correction, then correction precision is improved, but device complexity increases

Engineering Contradiction:

Improvedistortion correction precisionVSAvoidprocessing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential contour line segments from the captured image that are necessary for defining the quadrilateral distortion pattern. By focusing on extracting these specific geometric features rather than processing the entire image content, the system achieves precise distortion correction while keeping the processing complexity manageable through targeted feature extraction.

Inventive Principle:

Principle #2Taking out (Extraction)

4Measurement precision

If the method is limited to document images with detectable line segments, then line segment based correction is improved, but versatility decreases

Engineering Contradiction:

Improveline segment detection accuracyVSAvoidsubject type coverage

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent develops a universal distortion correction method that works across multiple subject types including document images, whiteboards, and other planar objects. By base the correction on fundamental geometric line segment detection rather than document-specific features, the system achieves multi-functionality and can handle various types of planar subjects that exhibit quadrilateral distortion patterns.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8731321B2Image processing device, image processing method, image processing program, and recording medium with recorded image processing program

Publication Date: 2014.05.20 SHARP KK

AI summary

An image processing device (10) includes: a line segment extracting section (14) for generating a line segment image obtained by extracting contour line segments contained in a contour of a subject in a captured image; a candidate quadrilateral calculating section (15) for (i) putting at least one virtual line segment in the line segment image (ii) selecting four line segments from a set containing the at least one virtual line segment and the contour line segments, and (iii) identifying a quadrilateral defined by four straight lines containing respective selected four line segments; and an image correcting section (17) for correcting a distortion in perspective transformation of the captured image based on the quadrilateral identified by the candidate quadrilateral calculating section (15). With the configuration, the distortion of the subject can be corrected without manually adjusting a degree of correction, even in a case where the subject having sides is partially not contained in the captured image or the subject is not a document image.