Grayscale Blob Detection

OpenMV Products
1

I would appreciate help in the format of the statement needed to detect “large” blobs in a grayscale image?

In my application, I am not interested in detecting color, rather, I want to detect larger objects regardless of their color.

For example, for the statement:

 img.find_blobs(thresholds, pixels_threshold=200, area_threshold=200)

What does one use for thresholds and pixels_threshold in this case? I am very new to OpenMV and would appreciate some help.

Thanks in advance.

2

If a blob’s bounding box area is less than area_threshold it is filtered out.

If a blob’s pixel count is less than pixel_threshold it is filtered out.

Please see the docs for the meaning of the args:

http://docs.openmv.io/library/omv.image.html?highlight=find_blobs#image.image.find_blobs

3

Thresholds is a list of grayscale upper and lower tuples.

[(100, 255), (0, 50)] and etc. All pixels with values in it are considered part of a blob, all pixels out of it are not the blob. The API is clear on this…

Pixels_threshold removes blobs that are too small (e.g. noise) from the list of output blobs if they don’t meet he pixel threshold. I.e. the number of connected pixels in the blob is less than the threshold.

4

Thank you gentlemen.