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FisFilter_ScanExactlyNEdges

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

Header:	FIL.h
Namespace:	fis

Locates a specified number of the strongest transitions between dark and bright pixels along a given path.

Syntax

void fis::FisFilter_ScanExactlyNEdges
(
	ScanExactlyNEdgesState& ioState,
	const fil::Image& inImage,
	const fil::Path& inScanPath,
	ftl::Optional<const fil::CoordinateSystem2D&> inScanPathAlignment,
	int inScanWidth,
	fil::InterpolationMethod::Type inImageInterpolation,
	const fil::EdgeScanParams& inEdgeScanParams,
	int inEdgeCount,
	fil::Selection::Type inEdgeSelection,
	float inMinDistance,
	ftl::Optional<float> inMaxDistance,
	ftl::Optional<const fil::LocalBlindness&> inLocalBlindness,
	ftl::Conditional<ftl::Array<fil::Edge1D> >& outEdges,
	ftl::Conditional<ftl::Array<fil::Gap1D> >& outGaps,
	ftl::Optional<fil::Path&> outAlignedScanPath = ftl::NIL,
	fil::Profile& diagBrightnessProfile,
	fil::Profile& diagResponseProfile,
	ftl::Array<fil::Path>& diagSamplingPoints,
	float& diagSamplingStep
)

Parameters

Name	Type	Range	Default	Description
ioState	ScanExactlyNEdgesState&			Object used to maintain state of the function.
inImage	const Image&			Input image to be measured
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 in extraction of image pixel values
inEdgeScanParams	const EdgeScanParams&		EdgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f MinMagnitude: 5.0f EdgeTransition: BrightToDark )	Parameters controlling the edge extraction process
inEdgeCount	int	0 -	1	Number of edges to be found
inEdgeSelection	Selection::Type			Selection mode of the resulting edges
inMinDistance	float	0.0 -	0.0f	Minimal distance between consecutive edges
inMaxDistance	Optional<float>	0.0 -	NIL	Maximal distance between consecutive edges
inLocalBlindness	Optional<const LocalBlindness&>		NIL	Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
outEdges	Conditional<Array<Edge1D> >&			Found edges
outGaps	Conditional<Array<Gap1D> >&			Gaps between consecutive edges
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
diagSamplingStep	float&			Used distance between consecutive sampling points on the scan path

Optional Outputs

The computation of following outputs can be switched off by passing value ftl::NIL to these parameters: outAlignedScanPath.

Description

The operation scans the image along inScanPath and finds a set of inEdgeCount image edges perpendicular to the path. If no subset (of inEdgeCount elements) of detected edges meets the requirements of inEdgeScanParams.minMagnitude, inMinDistance, inEdgeScanParams.edgeTransition 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.

Note that in case of a scan path which is closed, the parameters controlling the distances between consecutive found objects do not control the distance between the first and the last of the found objects (counting from the beginning of the scan path).

Hints

Set inEdgeCount to the number of edges that are to be found (the N number).
Define inEdgeScanParams.EdgeTransition to detect a particular edge type, and only that type.
If the expected number of edges cannot be 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.
Adjust inMinDistance (in pixels) to filter out false edges that appear in proximity to other edges.

Examples

FisFilter_ScanExactlyNEdges locates the edges across inScanPath (inEdgeCount = 61).

Remarks

Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.

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.