Circle Segmentor – Locate multiple overlapping circles

With Scorpion Vision we continuously make new tools or weapons in the quality war to help our customers improve their services. Our latest invention is tool # 153 – CircleSegmentor. The tool will be available in Scorpion 8.0 due january 2010. The basic specification is:

  • Locate multiple overlapping Circles
  • Sub-pixel accuracy
  • Intensity independent
  • Fast – multicore ready
  • Extensive Circle validation

The concept is basically:

  • Sobel-filter within a region of interest
  • Clever edge-decimation
  • RANSAC to locate circle candidates
  • PolygonMatch to verify and locate circles with sub-pixel accuracy

A test case for the tool is object counting and tracking in fish farming. The animation below shows an underwater image from a fish cage where Scorpion counts the pellets not eaten. To provide a proper counting an advanced tracking algorithm is used to follow each pellets and to collapse the multiple observations of each pellet to a single count. The CircleSegmentor provide the count and the center position of each pellets in every single frame.

is-2009-0020-A Realtime Object Counting and TrackingThe animations shows 2  images pr second – equalling the true speed.  A total of 32 pellets are counted in the 45 second animation.

We will “benchmark” the CircleSegmentor’s performance towards a blob approach.

Case # 1 is 10 pellets in the image. The CS counts 10 – blob segments 3 close pellets into one object.

is-2009-0021-A 10 circles
Case # 1 - CircleSegmentor counting 10 pellets

The corresponding blob image – blob 1 contains three pellets.

is-2009-0021-A 10 circles - 8 with blob
Case # 1 - Blob segments 3 pellets to one

Case # 2 – CircleSegmentor counts three overlapping pellets.

The image below shows how CS are able to count three overlapping objects. is-2009-0021-A segments 3

Case # 2 : CircleSegmentor segments 3 overlapping pellets

Object Counting and Tracking

is a large application area for machine vision. CircleSegmentor will find many applications within counting, tracking and robot vision and is an extremely useful extension of the power Scorpion toolbox. The sub-pixel accuracy is important for 3D stereo vision.

PolygonMatch is a trademark of Tordivel AS.

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