Blob analysis

Blobs are groups of pixels in an image with some shared properties (e.g. greyscale value).
Any blob analysis starts by identifying these areas in the image by using tools called blob detectors.

How does a blob detector work?

  • Turn the image into a set of binary images. If the image is in greyscale, the task is a simple thresholding on the image, while if the image is in colour, each channel will be thresholded independently. In the set of images, each one of them represents a thresholding operation at a different threshold.
  • The connected areas are identified in each binary image of the set.
Blob analysis
Blob analysis sample image
  • The blob coordinates are identified and grouped by threshold ranges.

Once the blobs have been identified, they can be analysed by calculating scalars such as:

  • Area
  • Perimeter
  • Convexity
  • Circularity
  • Compactness
Next →