Blob Detection

## Blob Detection

Extract regions in the image whose gray scale meets the set threshold, set screening conditions to screen regions, and set sorting methods to output regions in a certain sorting order

## Usage Scenarios
1. Coarse positioning of target objects in the image, output coordinates for use by the next module, such as optimizing feature matching.
2. Judgment of objects in the image, such as judging whether the object is the target object based on the area, rectangularity, circularity, or whether there are holes in the specified region in the image.

## Usage Method
Can be used as a single module or in combination with other modules.
![](/media/202602/2026-02-05_172740_9198620.36028948483076584.png)

### Usage Example
For example, to screen a single object that meets the area, select area in the screening conditions, set the minimum and maximum values, and objects stuck together will be excluded because the area is too large.
![](/media/202602/2026-02-05_172850_7509940.8626067546580284.png)

![](/media/202602/2026-02-05_172930_1041330.9138325715060368.png)

## Parameter Configuration Description
### Interface Parameters
Gray Threshold: Setting of gray value of gray image, regions meeting this interval are selected.
Total Count Judgment: Judgment of the final region result, if the number of regions is within this interval, the result is true, otherwise it is false.
Total Area Judgment: Judgment of the final region result, if the total area of all regions is within this interval, the result is true, otherwise it is false.
The logical relationship between Total Count Judgment and Total Area Judgment is "AND", if one is false, the output result is false.
Size Conversion: If enabled, convert the detected region size from pixel size to world coordinate size.
Learn Coordinate System: Learn the position of the first region.
![](/media/202602/2026-02-05_173107_8913580.18076151167493681.png)
### Advanced Parameters
Sort the detected region results, sorting can be ascending or descending according to area size, x, y coordinates.
![](/media/202602/2026-02-05_175959_7000070.7912503162104289.png)

![](/media/202602/2026-02-05_180008_0949070.012331619402523364.png)

### Screening Parameters
After the interface parameters give the threshold, all image regions meeting the threshold will be found. At this time, some regions can be filtered out according to some conditions, such as single area, center of gravity x, center of gravity y, center coordinate x/y of bounding rotated/upright rectangle, length and width of bounding rotated/upright rectangle, hole area, hole count, rectangularity, circularity, compactness, removing border regions, etc.

![](/media/202602/2026-02-05_180433_8108640.7076170386744366.png)

![](/media/202602/2026-02-05_180444_0015260.5135247309631629.png)

In order to facilitate setting parameter size, there is a blob info button next to it. Click to view the feature information of the detected blob regions. You can slide the horizontal scroll bar to view all features.

![](/media/202602/2026-02-05_180559_6676000.623175257591416.png)
## Output Description
Running Result: The module runs successfully, and if the output blob region meets the conditions, the result is true, otherwise it is false.
Blob Count: Total number of detected Blobs.
Blob Total Area: Total area of detected Blobs.
Blob Output: Detected Blob output, cannot be used as a mask by other modules.
Rotated Rectangle ROI: ROI output used by the module itself.
Mask Region: Mask output used.
Center of Gravity Array: Center of gravity of detected Blob regions, output as an array.
Rotated Rectangle Array: Array of minimum bounding rotated rectangles (center, width height, angle) of detected Blob regions.
Upright Rectangle Array: Array of minimum bounding upright rectangles (top-left coordinate, width height) of detected Blob regions.
Coordinate System: Learned coordinate system output.
![](/media/202602/2026-02-05_181336_0293720.8382481124931482.png)

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Click here to jump to the corresponding Chinese manual page: [Blob Detection](/doc/68)