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FitCircleToStripe


Header: AVL.h
Namespace: avl
Module: MetrologyPro

Performs a series 1D stripe detections and finds a circle that best matches the detected points.

Applications: Precise detection of ring-shaped objects, whose rough location is known beforehand.

Syntax

C++
C#
 
void avl::FitCircleToStripe
(
	const avl::Image& inImage,
	const avl::CircleFittingMap& inFittingMap,
	const StripeScanParams& inStripeScanParams,
	avl::Selection::Type inStripeSelection,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	float inMaxIncompleteness,
	avl::CircleFittingMethod::Type inFittingMethod,
	atl::Optional<MEstimator::Type> inOutlierSuppression,
	atl::Conditional<avl::Circle2D>& outCircle,
	atl::Conditional<avl::Circle2D>& outInnerCircle,
	atl::Conditional<avl::Circle2D>& outOuterCircle,
	atl::Optional<atl::Array<atl::Conditional<avl::Stripe1D>>&> outStripes = atl::NIL,
	atl::Optional<atl::Array<avl::Point2D>&> outStripePoints = atl::NIL,
	atl::Optional<atl::Conditional<avl::Profile>&> outDeviationProfile = atl::NIL,
	atl::Optional<atl::Array<avl::Profile>&> outBrightnessProfiles = atl::NIL,
	atl::Optional<atl::Array<avl::Profile>&> outResponseProfiles = atl::NIL
)

Parameters

Name Type Range Default Description
Input value inImage const Image& Image to fit the circle to
Input value inFittingMap const CircleFittingMap& Input fitting map
Input value inStripeScanParams const StripeScanParams& Parameters controlling the stripe extraction process
Input value inStripeSelection Selection::Type Selection::​Best Selection mode of stripe
Input value inLocalBlindness Optional<const LocalBlindness&> NIL Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
Input value inMaxIncompleteness float 0.0 - 0.999 0.1f Maximal fraction of stripe points not found
Input value inFittingMethod CircleFittingMethod::Type AlgebraicTaubin Method used to fit a circle
Input value inOutlierSuppression Optional<MEstimator::Type> NIL Selects a method for ignoring incorrectly detected points
Output value outCircle Conditional<Circle2D>& Fitted circle in the middle of found stripe
Output value outInnerCircle Conditional<Circle2D>& Fitted inner circle
Output value outOuterCircle Conditional<Circle2D>& Fitted outer circle
Output value outStripes Optional<Array<Conditional<Stripe1D>>&> NIL Found stripes
Output value outStripePoints Optional<Array<Point2D>&> NIL Extracted points of middle circle of an image stripe
Output value outDeviationProfile Optional<Conditional<Profile>&> NIL Profile of distances between the actual circle points and the corresponding reference circle points
Output value outBrightnessProfiles Optional<Array<Profile>&> NIL Extracted image profiles
Output value outResponseProfiles Optional<Array<Profile>&> NIL Profiles of the edge (derivative) operator response

Optional Outputs

The computation of following outputs can be switched off by passing value atl::NIL to these parameters: outStripes, outStripePoints, outDeviationProfile, outBrightnessProfiles, outResponseProfiles.

Read more about Optional Outputs.

Description

The operation tries to fit a given circle to stripe present in the inImage image. Internally, it performs a series of scans with the ScanSingleStripe filter using inFittingMap previously generated from the object being fitted. The found points are then used to determine the actual position of the circle in the image. Only inMaxIncompleteness fraction of these scans may fail. If the fitting according to the given parameters is not possible, outCircle is set to Nil.

Hints

  • Connect an input image to the inImage input.
  • Define inStripeScanParams.StripePolarity to detect a particular stripe type, and only that type.
  • Adjust inStripeScanParams.MinStripeWidth and inStripeScanParams.MaxStripeWidth to the expected thickness of the stripe (in pixels).
  • If no or too few stripe points are found, try decreasing inStripeScanParams.MinMagnitude.
  • If some of the scans may fail, set the inMaxIncompleteness input accordingly.
  • If some of the scans may produce false results, try different values of the inOutlierSuppression input.
  • Use the outStripePoints outputs to visualize the scanning results.

Examples

Fitting a circle to the dark circular stripe of a washer
(inStripeScanParams.Polarity = Dark).

Remarks

Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.

This filter is a part of the Shape Fitting toolset. To read more about this technique, one can refer to the Shape Fitting chapter of our Machine Vision Guide

Hardware Acceleration

This operation supports automatic parallelization for multicore and multiprocessor systems.

See Also

  • FitCircleToEdges – Performs a series of 1D edge detections and finds a circle that best matches the detected points.
  • FitCircleToRidges – Performs a series of 1D ridge detections and finds a circle that best matches the detected points.
  • FitCircleToStripe_Direct – Performs a series 1D stripe detections and finds a circle that best matches the detected points.