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MeasureObjectWidth

Measures the width of an object using stripe detection.

Header:	AVL.h

Syntax

void avl::MeasureObjectWidth
(
	const avl::Image& inImage,
	const atl::Array<avl::ScanMap>& inMeasurementMap,
	const avl::StripeScanParams& inStripeScanParams,
	avl::MeasureObjectMethod::Type inMeasureMethod,
	avl::Selection::Type inStripeSelection,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	atl::Optional<avl::MEstimator::Type> inOutlierSuppression,
	int inOutlierCount,
	atl::Conditional<float>& outObjectWidth,
	atl::Conditional<avl::Segment2D>& outSegment1,
	atl::Conditional<avl::Segment2D>& outSegment2,
	atl::Array<avl::Point2D>& diagPoints1,
	atl::Array<avl::Point2D>& diagPoints2
)

void MeasureObjectWidth
(
	Image inImage,
	ScanMap[] inMeasurementMap,
	StripeScanParams inStripeScanParams,
	MeasureObjectMethod inMeasureMethod,
	Selection inStripeSelection,
	LocalBlindness? inLocalBlindness,
	MEstimator? inOutlierSuppression,
	int inOutlierCount,
	out float? outObjectWidth,
	out Segment2D? outSegment1,
	out Segment2D? outSegment2,
	out Point2D[] diagPoints1,
	out Point2D[] diagPoints2
)

Parameters

Name	Type	Default	Description
inImage	const Image&		Input image
inMeasurementMap	const Array<ScanMap>&		Input measurement map
inStripeScanParams	const StripeScanParams&		Parameters controlling the object stripe extraction process
inMeasureMethod	MeasureObjectMethod::Type		Method used to measure the object
inStripeSelection	Selection::Type	Selection::Best	Selection mode of edges of the object
inLocalBlindness	Optional<const LocalBlindness&>	NIL	Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
inOutlierSuppression	Optional<MEstimator::Type>	NIL	Selects a method for ignoring incorrectly detected points
inOutlierCount	int		Determines how many outlying points are rejected before the width is measured
outObjectWidth	Conditional<float>&		Width of the object
outSegment1	Conditional<Segment2D>&		First edge of the object
outSegment2	Conditional<Segment2D>&		Second edge of the object
diagPoints1	Array<Point2D>&		Detected edge points on the first side
diagPoints2	Array<Point2D>&		Detected edge points on the second side

Description

The filter measures the width of an object present in an image. Internally, it performs a series of scans with ScanSingleStripe filter using inMeasurementMap and inStripeScanParams. The so obtained points are then used for computing two parallel segments by means of a slightly modified segment fitting routine. The process is supported by inOutlierSuppression parameter. Finally, having the aforementioned stripe widths and fitted segments' direction, the object width can be computed using a selected inMeasureMethod method. The inOutlierCount stripe widths most differing from the median width are not used in this step. The inMeasurementMap should be created with CreateMeasurementMap function. For the filter to work properly, the scan segments do not have to be necessarily perpendicular to the object edges.

Hints

Define inStripeScanParams.StripePolarity to detect a particular edge type, and only that type.
If some points (diagPoints1, diagPoints2) are not found, try decreasing inStripeScanParams.MinMagnitude.
If the object is more narrow than 6 pixels, change inStripeScanParams.ProfileInterpolation to Quadratic3.
Experiment with inOutlierSuppression and inOutlierCount to deal with some amount of incorrectly detected points.
Experiment with various values for inMeasureMethod to obtain best possible precision.

Examples

MeasureObjectWidth performed on the sample image. Green segments are diagScanSegments, the other two are the found object edges.

Errors

Error type	Description
DomainError	Invalid MeasurementMap in MeasureObjectWidth function. Use CreateMeasurementMap function to create it properly.