AI-assisted engineering drawing change detection using alignment, ROI comparison, OCR extraction, and token analysis.
Engineering teams often spend significant time manually comparing drawing revisions to identify changes in views, notes, labels, and other document elements. This project presents a prototype system that automates part of that process using computer vision and OCR-based comparison techniques.
The system was developed as an experimental workflow to support engineering drawing review and change detection.
- Drawing alignment before comparison
- Global pixel-based difference analysis
- ROI-based localized comparison
- OCR extraction from notes block
- Token normalization and comparison
- Change classification
- Evaluation using precision, recall, accuracy, and confusion matrix
- Image alignment
- Pixel difference detection
- ROI template matching
- OCR text extraction
- Engineering token comparison
- Similarity scoring
- PASS / CHANGE classification
- Load old and new drawing files
- Align drawings
- Apply ROI templates
- Measure ROI-wise pixel change
- Run OCR on selected text regions
- Normalize extracted text
- Compare tokens and labels
- Generate final engineering change summary
- Evaluate performance using metrics
- Section view change detection
- Front face / side view comparison
- Notes block OCR difference
- ROI-based classification report
- Confusion matrix and evaluation charts
The prototype was evaluated using:
- Precision
- Recall
- Accuracy
- ROI classification accuracy
- Confusion matrix analysis
- Token detection performance
- OCR performance depends on drawing clarity
- Small symbol-level changes may require stronger detection logic
- ROI templates are currently predefined
- Performance may vary with scan quality and layout variation
- automatic dimension detection
- weld symbol detection
- dynamic ROI generation
- better engineering OCR pipeline
- change severity classification
- integration with CAD/PDM workflows
Ramu Gopal
Founder, The Tech Thinker
Senior Mechanical Design Engineer | CAD Automation | Engineering AI Workflows
- The Tech Thinker article: [https://thetechthinker.com/engineering-drawing-change-detection/]
- Medium article: [https://medium.com/@TheTechThinker/engineering-drawing-change-detection-using-computer-vision-15b5fb9d8c6e]
This repository is a research and portfolio prototype intended for educational and technical demonstration purposes.