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FitArcToStripe


Header: AVL.h
Namespace: avl
Module: MetrologyPro

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

Applications: Precise detection of a ring section, whose rough location is known beforehand.

Syntax

C++
C#
 
void avl::FitArcToStripe
(
	const avl::Image& inImage,
	const avl::ArcFittingMap& inFittingMap,
	const StripeScanParams& inStripeScanParams,
	avl::Selection::Type inStripeSelection,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	float inMaxIncompleteness,
	avl::CircleFittingMethod::Type inFittingMethod,
	atl::Optional<avl::MEstimator::Type> inOutlierSuppression,
	atl::Conditional<avl::Arc2D>& outArc,
	atl::Conditional<avl::Arc2D>& outInnerArc,
	atl::Conditional<avl::Arc2D>& outOuterArc,
	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& Input image to fit arc to
Input value inFittingMap const ArcFittingMap& 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 an arc
Input value inOutlierSuppression Optional<MEstimator::Type> NIL Selects a method for ignoring incorrectly detected points
Output value outArc Conditional<Arc2D>& Fitted arc in the middle of found stripe
Output value outInnerArc Conditional<Arc2D>& Fitted inner arc
Output value outOuterArc Conditional<Arc2D>& Fitted outer arc
Output value outStripes Optional<Array<Conditional<Stripe1D>>&> NIL Found stripes
Output value outStripePoints Optional<Array<Point2D>&> NIL Extracted points of middle arc of an image stripe
Output value outDeviationProfile Optional<Conditional<Profile>&> NIL Profile of distances between the actual arc points and the corresponding reference arc 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 arc 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 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 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 an arc to the dark stripe formed on one side of a hole
(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

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