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FitArcToEdges


Header: AVL.h
Namespace: avl
Module: MetrologyPro

Performs a series of 1D edge detections and finds an arc that best matches the detected points.

Applications: Precise detection of an arciform edge, whose rough location is known beforehand.

Syntax

C++
C#
 
void avl::FitArcToEdges
(
	const avl::Image& inImage,
	const avl::ArcFittingMap& inFittingMap,
	const EdgeScanParams& inEdgeScanParams,
	avl::Selection::Type inEdgeSelection,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	float inMaxIncompleteness,
	avl::CircleFittingMethod::Type inFittingMethod,
	atl::Optional<avl::MEstimator::Type> inOutlierSuppression,
	atl::Conditional<avl::Arc2D>& outArc,
	atl::Optional<atl::Array<atl::Conditional<avl::Edge1D>>&> outEdges = atl::NIL,
	atl::Optional<atl::Conditional<avl::Profile>&> outDeviationProfile = atl::NIL,
	atl::Optional<atl::Array<avl::Point2D>&> outInliers = 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& Input image to fit arc to
Input value inFittingMap const ArcFittingMap& Input fitting map
Input value inEdgeScanParams const EdgeScanParams& Parameters controlling the edge extraction process
Input value inEdgeSelection Selection::Type Selection::​Best Selection mode of edges
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 edge points not found
Input value inFittingMethod CircleFittingMethod::Type AlgebraicTaubin Method used to fit an arc
Input value inOutlierSuppression Optional<MEstimator::Type> NIL Selects a method for ignoring incorrectly detected points
Output value outArc Conditional<Arc2D>& Fitted arc or nothing if the fitting fails
Output value outEdges Optional<Array<Conditional<Edge1D>>&> NIL Found edges
Output value outDeviationProfile Optional<Conditional<Profile>&> NIL Profile of distances between the actual arc points and the corresponding reference arc points
Output value outInliers Optional<Array<Point2D>&> NIL Points matching the fitting arc
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: outEdges, outDeviationProfile, outInliers, outBrightnessProfiles, outResponseProfiles.

Read more about Optional Outputs.

Description

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

Hints

  • Connect an input image to the inImage input.
  • Define inEdgeScanParams.EdgeTransition to detect a particular edge type, and only that type.
  • If no or too few edge points are found, try decreasing inEdgeScanParams.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 outEdges outputs to visualize the scanning results.

Examples

Fitting an arc to the edges of a semi-hole
(inEdgeScanParams.Transition = BrightToDark).

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

  • CreateArcFittingMap – Precomputes a data object that is required for fast arc fitting on images.
  • FitArcToRidges – Performs a series of 1D ridge detections and finds an arc that best matches the detected points.
  • FitArcToStripe – Performs a series of 1D stripe detections and finds an arc that best matches the detected points.
  • FitArcToEdges_Direct – Performs a series of 1D edge detections and finds an arc that best matches the detected points.