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# AvsFilter_FitCircleToEdges

This is Filter Equivalent. This function may be present in generated code, but should not be used in hand-written code. CreateCircleFittingMap and FitCircleToEdges should be used instead.

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

### Syntax

void avs::AvsFilter_FitCircleToEdges
(
FitCircleToEdgesState& ioState,
const avl::Image& inImage,
const avl::CircleFittingField& inFittingField,
atl::Optional<const avl::CoordinateSystem2D&> inFittingFieldAlignment,
int inScanCount,
int inScanWidth,
const avl::InterpolationMethod::Type inImageInterpolation,
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::Circle2D>& outCircle,
atl::Optional<atl::Array<atl::Conditional<avl::Edge1D> >&> outEdges = 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
ioState FitCircleToEdgesState& Object used to maintain state of the function.
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)
inImageInterpolation const InterpolationMethod::Type Bilinear Interpolation method used for extraction of image pixel values
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 a circle
inOutlierSuppression Optional<MEstimator::Type> NIL Selects a method for ignoring incorrectly detected points
outCircle Conditional<Circle2D>& Fitted circle 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 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: outCircle, outEdges, outDeviationProfile, outAlignedFittingField.

### Description

The operation tries to fit a given circle to edges present in the inImage image. Internally, it performs a series of scans with the ScanSingleEdge 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 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 a circles to the edges of a hole
(inEdgeScanParams.Transition = BrightToDark).