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AvsFilter_ScanSingleEdge

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

Locates the strongest transition between dark and bright pixels along a given path.

Header:	AVL.h

Syntax

void avs::AvsFilter_ScanSingleEdge
(
	ScanSingleEdgeState& ioState,
	const avl::Image& inImage,
	const avl::Path& inScanPath,
	atl::Optional<const avl::CoordinateSystem2D&> inScanPathAlignment,
	int inScanWidth,
	avl::InterpolationMethod::Type inImageInterpolation,
	const avl::EdgeScanParams& inEdgeScanParams,
	avl::Selection::Type inEdgeSelection,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	atl::Conditional<avl::Edge1D>& outEdge,
	atl::Optional<avl::Path&> outAlignedScanPath = atl::NIL,
	avl::Profile& diagBrightnessProfile,
	avl::Profile& diagResponseProfile,
	atl::Array<avl::Path>& diagSamplingPoints
)

Parameters

Name	Type	Range	Default	Description
ioState	ScanSingleEdgeState&			Object used to maintain state of the function.
inImage	const Image&			Input image
inScanPath	const Path&			Path along which the scan is performed
inScanPathAlignment	Optional<const CoordinateSystem2D&>		NIL	Adjusts the scan path to the position of the inspected object
inScanWidth	int	1 -	5	Width of the scan field in pixels
inImageInterpolation	InterpolationMethod::Type		Bilinear	Interpolation method used for extraction of image pixels
inEdgeScanParams	const EdgeScanParams&		EdgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f MinMagnitude: 5.0f EdgeTransition: BrightToDark )	Parameters controlling the edge extraction process
inEdgeSelection	Selection::Type			If many edge points are possible, defines which one is selected
inLocalBlindness	Optional<const LocalBlindness&>		NIL	Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
outEdge	Conditional<Edge1D>&			Found edge
outAlignedScanPath	Optional<Path&>		NIL	Path along which the scan is performed; in the image coordinate system
diagBrightnessProfile	Profile&			Extracted image profile
diagResponseProfile	Profile&			Profile of the edge (derivative) operator response
diagSamplingPoints	Array<Path>&			Array of paths each one containing the sampling points that contributed to a single value of the extracted profile

Description

The operation scans the image along inScanPath and locates the strongest edge perpendicular to the path. If the strongest edge is weaker than inEdgeScanParams.minMagnitude then the outputs are set to NIL.

The optional parameter inScanPathAlignment defines a transform to be performed on the inScanPath so that the actual scan path (outAlignedScanPath) is adjusted to the position of the object, typically detected by one of Template Matching filters.

Hints

Define inEdgeScanParams.EdgeTransition to detect a particular edge type, and only that type.
If no edge is found, try decreasing inEdgeScanParams.MinMagnitude. Verify this with the values on the diagResponseProfile output.
If consecutive edges are closer than 6 pixels apart, change inEdgeScanParams.ProfileInterpolation to Quadratic3.

Examples

AvsFilter_ScanSingleEdge locates the strongest edge across inScanPath.

Remarks

For more information about local coordinate systems please refer to the following article.

This filter is a part of the 1D Edge Detection toolset. For a comprehensive introduction to this technique please refer to 1D Edge Detection and 1D Edge Detection - Subpixel Precision chapters of our Machine Vision Guide.