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# AvsFilter_FitCircleToStripe

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

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

### Syntax

void avs::AvsFilter_FitCircleToStripe
(
FitCircleToStripeState& 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::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
ioState FitCircleToStripeState& 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
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: outCircle, outInnerCircle, outOuterCircle, 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 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).