Document Comparison Using Reference Point Alignment

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Solution Overview

Problem

The challenge in document revision tracking is aligning modified and original documents for accurate difference identification, especially when one version is generated directly from an application and the other is scanned from a printed copy, which often introduces distortions like rotation, scale, and offset, making it difficult to track changes effectively.

Innovation Solution

A method that involves displaying both documents on a monitor, allowing users to select reference points for transforming bitmaps to a common reference, enabling precise alignment and comparison, with indicia displayed to highlight differences between the original and modified documents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If documents are scanned from printed copies for revision tracking, then document exchange and collaboration are facilitated, but distortions such as rotation, scale, and offset are introduced, making accurate difference identification difficult

Engineering Contradiction:

Improvedocument exchange capabilityVSAvoiddifference identification accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent introduces reference points as intermediary elements that are placed on both the original and scanned documents. These reference points serve as mediators to establish correspondence between the two documents, enabling the system to calculate transformation parameters (rotation, scale, offset) that align the scanned document with the original, thereby resolving the distortion problem while maintaining document exchange versatility

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent transforms the scanned document by changing its geometric parameters (rotation angle, scale factor, offset position) based on the calculated transformation parameters derived from reference point correspondence. This parameter adjustment aligns the distorted scanned document with the original document, enabling accurate difference identification while preserving the ability to exchange documents in various formats

Inventive Principle:

Principle #35Parameter changes

2Productivity

If automatic alignment methods are used to compare documents, then processing speed is improved, but false positives from pixel noise and distortion increase

Engineering Contradiction:

Improvedocument comparison speedVSAvoiddifference detection accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent performs preliminary alignment of the scanned document with the original document before conducting the difference comparison. By calculating transformation parameters from reference points and applying alignment transformations in advance, the system eliminates the need for complex noise filtering during comparison, achieving both high processing speed and high reliability in difference detection

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses the reference points that are already present on the documents (selected by users or automatically detected) to self-align the documents without requiring external calibration data or complex iterative optimization algorithms. This self-service alignment approach maintains processing efficiency while significantly improving the reliability of subsequent difference detection

Inventive Principle:

Principle #25Self-service

3Measurement precision

If manual alignment methods are used to account for distortion, then alignment accuracy is improved, but user time and operational complexity increase

Engineering Contradiction:

Improvealignment accuracyVSAvoiduser operation simplicity

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent requires users to select only a limited number of key reference points (e.g., corners or distinctive features) rather than manually adjusting the entire document or selecting numerous points. This partial action approach achieves sufficient alignment accuracy for most practical cases while keeping the operation simple and quick, balancing alignment precision with ease of use

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS7971149B2Method for comparing an original document and a modified document using user-selected reference point sets

Publication Date: 2011.06.28 BLUEBEAM INC

AI summary

A method for emphasizing differences between original and modified documents. The method includes displaying the original document with the original document defining an original document boundary and a first bitmap. The method includes displaying the modified document with the modified document defining a modified document boundary and a second bitmap. The method includes receiving a user-selected first reference point set including a plurality of reference points correlated to coordinates within the original document boundary. The method includes receiving a user-selected second reference point set including a plurality of reference points correlated to coordinates within the modified document boundary. The method includes transforming the first bitmap to a common reference using the first reference point set. The method includes transforming the second bitmap to the common reference using the second reference point set. The method includes comparing the bitmaps. The method includes displaying indicia related to the comparison of the bitmaps.