Blob Detector

This function block detects blob-like features (bright/dark roundish objects) in an image. Use the sliders to tune detection sensitivity and shape filters so the block finds only the blobs you care about.

📥 Inputs

Image Any Image to analyze for blobs.

📤 Outputs

Image Any Visual result image with detected blobs marked. Number of Blobs Count of detected blobs. Blobs Positions List of blob center positions (x, y). Blobs Sizes Sizes (diameter) of detected blobs.

🕹️ Controls

Threshold Range Minimum and maximum intensity thresholds used to detect candidate blobs. Area Range Minimum and maximum blob area as a percentage of the image scale. Circularity Range Allowed circularity range to favor round shapes. Convexity Range Allowed convexity range to exclude highly concave shapes. Inertia Range Allowed inertia ratio range to filter elongated vs. round blobs.

🎯 Features

• Visual feedback: detected blobs are drawn on the output image so you can inspect results immediately.

• Shape filtering: narrow detections using area, circularity, convexity and inertia sliders to reduce false positives.

• Live tuning: slider adjustments take effect on the next evaluation so you can iterate quickly.

📝 Usage Instructions

1. Provide an image to Image Any.

2. Start with a broad Threshold Range and adjust until most blob candidates appear on the output image.

3. Use Area Range to remove very small or very large detections relative to your object size.

4. Tune Circularity Range, Convexity Range and Inertia Range to exclude shapes that are not blob-like.

5. Inspect results in the output image and read the numeric outputs for automation or logging.

📊 Evaluation

When run, the block analyzes the input image and returns a marked image plus the number, positions and sizes of detected blobs. Use these outputs downstream for measurement, counting or decision logic.

💡 Tips and Tricks

• Preprocess noisy images with Blur or Denoising to reduce spurious small detections.

• Convert complex scenes to a clearer foreground with Image Threshold or HSV Filter before feeding this block.

• If you only need to analyze a region, crop first using Image ROI Select to speed up detection and avoid background blobs.

• For large images, try Image Resizer to lower resolution and increase processing speed while keeping meaningful blob sizes.

• Visualize or save results using Show Image and Image Logger when tuning or to keep records.

• Combine with drawing blocks such as Draw Detections to overlay counts or rectangular markers on the image for operator displays.

(hint: use these related blocks to improve robustness and speed: Blur, Image Threshold, Image ROI Select, Image Resizer, Denoising, Show Image, Image Logger, Draw Detections)

🛠️ Troubleshooting

• No blobs detected: widen the Threshold Range and increase the Area Range; check the input image contrast.

• Too many small false blobs: increase the minimum in Area Range or apply Blur / Image Threshold to remove noise.

• Detecting elongated or irregular shapes: tighten Circularity Range and/or adjust Inertia Range to favor round blobs.

• Inconsistent detections across frames: use consistent lighting, or apply preprocessing (Auto Contrast / Denoising) to stabilize input images.