Image Inclination Angle Detection Using Character Centroid Clustering

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Solution Overview

Problem

Existing methods for detecting the inclination angle of an image, such as using regression lines or edge extraction, are inaccurate when dealing with documents that are slanted, particularly when characters have different heights or are arranged in vertical typesetting, leading to poor print quality.

Innovation Solution

An image inclination angle detection apparatus and program that sets search points on characters, generates search frames, detects line space regions, and calculates approximate straight lines to determine the inclination angle of the image, using clustering and principal component analysis to improve accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If regression line method is used to detect inclination angle, then the detection process is simple, but the detection precision deteriorates when characters have different heights or vertical typesetting

Engineering Contradiction:
Improvedetection process complexityVSAvoidinclination angle detection precision
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent segments the document image into multiple character regions and processes each region independently to detect inclination angles. Instead of treating the entire document as a single entity, the method divides it into character blocks, detects local inclinations, and then synthesizes the overall inclination angle, thereby improving precision for documents with varied character heights and layouts.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent transitions from a one-dimensional regression line approach to a two-dimensional analysis by examining character distributions across multiple regions. It uses spatial coordinates of character centroids and applies geometric transformations to detect inclination angles more accurately, adding dimensional depth to the detection process.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If edge extraction and thinning processing is performed to detect inclination angle, then the detection can handle various character layouts, but the processing complexity and time increase

Engineering Contradiction:
Improvehandling capability for various character layoutsVSAvoidprocessing complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent performs preliminary actions by first detecting character positions and centroids before inclination angle detection. It pre-processes the image to identify and mark character regions, which simplifies subsequent inclination detection by providing ready-to-use coordinate data, thereby reducing overall processing complexity while maintaining versatility.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex mechanical edge extraction and thinning operations with a more efficient computational approach using character centroid detection and geometric transformation. Instead of manually extracting edges through multiple processing steps, it uses coordinate-based methods and mathematical transformations to achieve the same goal with reduced complexity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If traditional methods are used for inclination detection, then the processing speed is fast, but the print quality deteriorates due to inaccurate inclination angles

Engineering Contradiction:
Improveprocessing speedVSAvoidprint quality
Core Design Contradiction:
ProductivityVSManufacturing precision

Solution Approach 1:

The patent implements self-service by using the document's own character structures to determine the inclination angle. It extracts features directly from the document content itself (character positions, centroids, and distributions) rather than relying on external reference lines or markers, enabling accurate and rapid inclination detection that directly improves print quality.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent changes key parameters from traditional methods by using character centroid coordinates and spatial distributions instead of edge pixel coordinates. It transforms the inclination detection problem into a parameter-based geometric calculation using character positions, which maintains processing speed while significantly improving accuracy and resulting print quality.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS10911636B2Image inclination angle detection apparatus that detects inclination angle of image with respect to document, image forming apparatus, and computer-readable non-transitory recording medium storing image inclination angle detection program
Publication Date: 2021.02.02 KYOCERA DOCUMENT SOLUTIONS INC
  • US10911636B2 patent drawing
  • US10911636B2 patent drawing
  • US10911636B2 patent drawing

AI summary

A control device sets first points on characters, generates a first frame composed of a first point and first circles, attaches first marks to points at which the first circles intersect characters, detects a range having a largest central angle and no first marks, sets second points on the first circles in the detected region, generates a second frame composed of a second point and second circles, attaches second marks to points at which the second circles intersect characters, sets a direction passing through the center portions of ranges having no second marks and the second point, sets second points arranged in the direction as the same class, calculates an approximate line connecting second points for each class, obtains straight lines indicating a row direction of characters immediately above and below an approximate line, and determines an inclination angle of an image from inclinations of the straight lines.