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FitCircleToStripe_Direct

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

void avl::FitCircleToStripe_Direct
(
	const avl::Image& inImage,
	const avl::CircleFittingField& inFittingField,
	atl::Optional<const avl::CoordinateSystem2D&> inFittingFieldAlignment,
	int inScanCount,
	int inScanWidth,
	const avl::SamplingParams& inSamplingParams,
	const avl::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::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<avl::CircleFittingField&> outAlignedFittingField = atl::NIL,
	atl::Array<avl::Segment2D>& diagScanSegments,
	atl::Array<avl::Rectangle2D>& diagSamplingAreas,
	atl::Array<avl::Profile>& diagBrightnessProfiles,
	atl::Array<avl::Profile>& diagResponseProfiles
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Image to fit the circle to
inFittingField	const CircleFittingField&			Circle fitting field
inFittingFieldAlignment	Optional<const CoordinateSystem2D&>		NIL	Adjusts the fitting field to the position of the inspected object
inScanCount	int	3 -	10	The number of points that will be searched to estimate the position of the circle
inScanWidth	int	1 -	5	The width of each scan field (in pixels)
inSamplingParams	const SamplingParams&			Parameters controlling the sampling process
inStripeScanParams	const StripeScanParams&		StripeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f MinMagnitude: 5.0f MaxInnerEdgeMagnitude: Nil StripePolarity: Dark MinStripeWidth: 0.0f MaxStripeWidth: Nil )	Parameters controlling the stripe extraction process
inStripeSelection	Selection::Type			Selection mode of stripe
inLocalBlindness	Optional<const LocalBlindness&>		NIL	Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
inMaxIncompleteness	float	0.0 - 0.999	0.1f	Maximal fraction of stripe points not found
inFittingMethod	CircleFittingMethod::Type		AlgebraicTaubin	Method used to fit a circle
inOutlierSuppression	Optional<MEstimator::Type>		NIL	Selects a method for ignoring incorrectly detected points
outCircle	Conditional<Circle2D>&			Fitted circle in the middle of found stripe
outInnerCircle	Conditional<Circle2D>&			Fitted inner circle
outOuterCircle	Conditional<Circle2D>&			Fitted outer circle
outStripes	Optional<Array<Conditional<Stripe1D> >&>		NIL	Found stripes
outStripePoints	Optional<Array<Point2D>&>		NIL	Extracted points of middle circle of an image stripe
outDeviationProfile	Optional<Conditional<Profile>&>		NIL	Profile of distances between the actual circle points and the corresponding reference circle points
outAlignedFittingField	Optional<CircleFittingField&>		NIL	Fitting field used; in the image coordinate system
diagScanSegments	Array<Segment2D>&			Segments along which the scans were run
diagSamplingAreas	Array<Rectangle2D>&			Areas from which the input image is sampled
diagBrightnessProfiles	Array<Profile>&			Extracted image profiles
diagResponseProfiles	Array<Profile>&			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, outAlignedFittingField.

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_Direct filter along inScanCount specific scan segments which length is always equal to the inFittingField width and cannot be less than 4. 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.