Background estimation is a common challenge in image processing and machine vision, especially in dynamic environments such as traffic monitoring or automated production lines. One simple yet effective solution is median filtering.
Basic Median Method
Imagine a highway with moving cars. The background (road, trees, signs) is visible most of the time, while cars appear as outliers. A median filter calculates the median of each pixel over a series of frames (e.g., last 50 images) to generate a stable background image. Tools like Halcon’s rank_image function simplify this process.
- Results: Most of the background is accurately reconstructed, but occasional artifacts may appear in areas frequently occupied by moving objects.
Improved Approach
To reduce artifacts:
- Only include pixels in the median calculation if intensity changes between consecutive frames are below a threshold (e.g., 50).
- Randomize pixel values temporarily to avoid clustering around moving objects.
This method stabilizes the background faster and improves detection in partially congested scenes.
Advanced Considerations
In highly dynamic or congested scenes, a median filter may not fully resolve the problem. Alternative strategies, such as selecting the most common pixel value in a histogram instead of the median, can further enhance results.
Business Benefits for Automation and Quality Control
- Improved object detection by stabilizing dynamic backgrounds
- Reduced false positives in automated inspection or surveillance
- Optimized machine vision systems for high-speed production or monitoring
- Faster and more reliable analysis using Halcon or similar computer vision libraries
Conclusion
Median-based background estimation is a practical and efficient technique for many machine vision and computer vision applications. By applying improved methods, systems can maintain high detection accuracy even in dynamic environments.
Want to optimize your machine vision system with advanced background estimation?
Contact us at info@subpixel.hr to learn how Subpixel can enhance your computer vision solutions for automation and quality control.
