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Header: AVL.h
Namespace: avl
Module: FoundationBasic

Finds the strongest circle of a given radius in the input image.

Applications: Detection of a circular or close-to-circular object like a hole, pin, pill or particle.


void avl::DetectSingleCircle
	const avl::Image& inImage,
	atl::Optional<const avl::Region&> inRoi,
	float inRadius,
	float inMinScore,
	float inEdgeThreshold,
	atl::Conditional<avl::HoughCircle>& outCircle,
	avl::Image& diagGradientMagnitudeImage,
	avl::Image& diagScoreImage


Name Type Range Default Description
Input value
inImage const Image& Input image
Input value
inRoi Optional<const Region&> NIL Input region of interest
Input value
inRadius float 0.0 - 10.0f Circle's radius
Input value
inMinScore float 0.0 - 20.0f Minimum matching score
Input value
inEdgeThreshold float 10.0f Minimum accepted edge magnitude
Output value
outCircle Conditional<HoughCircle>& Found circle
Diagnostic input
diagGradientMagnitudeImage Image& Visualized gradients magnitude of an input image
Diagnostic input
diagScoreImage Image& Calculated score for each pixel of an input image


The operation detects circular object of given radius (in pixels) in the inImage using the Hough Transform approach.


  • Pass an input image to the inImage input.
  • Define the expected circle radius on the inRadius input.
  • Set inEdgeThreshold to define the minimum strength of edges that will be taken into account. Verify this value with the diagGradientMagnitudeImage output.
  • Experimentally set the inMinScore value, whose meaning is more or less "the number of pixels voting for a particular object location".


DetectSingleCircle performed on the sample image.

Hardware Acceleration

This operation supports automatic parallelization for multicore and multiprocessor systems.

See Also

  • DetectLines – Finds lines in an image using Hough Transform.
  • DetectPaths – Finds a specified shape in an image using Hough Transform.
  • DetectSegments – Finds segments in an image using Hough Transform.