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FitArcToEdges_Direct

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

void avl::FitArcToEdges_Direct
(
	const avl::Image& inImage,
	const avl::ArcFittingField& inFittingField,
	atl::Optional<const avl::CoordinateSystem2D&> inFittingFieldAlignment,
	int inScanCount,
	int inScanWidth,
	const avl::SamplingParams& inSamplingParams,
	const avl::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<avl::ArcFittingField&> outAlignedFittingField = atl::NIL,
	atl::Optional<atl::Array<avl::Point2D>&> outInliers = 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&			Input image to fit arc to
inFittingField	const ArcFittingField&			Arc 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 arc
inScanWidth	int	1 -	5	The width of each scan field (in pixels)
inSamplingParams	const SamplingParams&			Parameters controlling the sampling process
inEdgeScanParams	const EdgeScanParams&		EdgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 1.0f MinMagnitude: 5.0f EdgeTransition: BrightToDark )	Parameters controlling the edge extraction process
inEdgeSelection	Selection::Type			Selection mode of edges
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 edge points not found
inFittingMethod	CircleFittingMethod::Type		AlgebraicTaubin	Method used to fit an arc
inOutlierSuppression	Optional<MEstimator::Type>		NIL	Selects a method for ignoring incorrectly detected points
outArc	Conditional<Arc2D>&			Fitted arc or nothing if the fitting fails
outEdges	Optional<Array<Conditional<Edge1D> >&>		NIL	Found edges
outDeviationProfile	Optional<Conditional<Profile>&>		NIL	Profile of distances between the actual arc points and the corresponding reference arc points
outAlignedFittingField	Optional<ArcFittingField&>		NIL	Fitting field used; in the image coordinate system
outInliers	Optional<Array<Point2D>&>		NIL	Points matching the fitting arc
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: outEdges, outDeviationProfile, outAlignedFittingField, outInliers.

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_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 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.