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ScanSingleEdge_Direct

Header:	AVL.h
Namespace:	avl
Module:	MetrologyBasic

Locates the strongest transition between dark and bright pixels along a given path (without a scan map).

Applications: Very fast detection of an object (e.g. horizontal displacement of a bottle) and simple measurements (e.g. liquid level in a bottle).

Syntax

void avl::ScanSingleEdge_Direct
(
	const avl::Image& inImage,
	const avl::Path& inScanPath,
	atl::Optional<const avl::CoordinateSystem2D&> inScanPathAlignment,
	int inScanWidth,
	const avl::SamplingParams& inSamplingParams,
	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,
	atl::Optional<avl::Profile&> outBrightnessProfile = atl::NIL,
	atl::Optional<avl::Profile&> outResponseProfile = atl::NIL,
	atl::Array<avl::Path>& diagSamplingPoints,
	float& diagSamplingStep
)

Parameters

Name	Type	Range	Default	Description
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
inSamplingParams	const SamplingParams&		SamplingParams ( Interpolation: Bilinear SamplingStep: 1.0f SampleCount: Nil )	Parameters controlling the sampling process
inEdgeScanParams	const EdgeScanParams&		EdgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f MinMagnitude: 5.0f EdgeTransition: BrightToDark )	Parameters controlling the edge extraction process
inEdgeSelection	Selection::Type			Selection mode of the resulting edge
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	Transformed input path
outBrightnessProfile	Optional<Profile&>		NIL	Extracted image profile
outResponseProfile	Optional<Profile&>		NIL	Profile of the edge (derivative) operator response
diagSamplingPoints	Array<Path>&			Array of paths each one containing the sampling points that contributes 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 atl::NIL to these parameters: outAlignedScanPath, outBrightnessProfile, outResponseProfile.

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 outResponseProfile output.
If consecutive edges are closer than 6 pixels apart, change inEdgeScanParams.ProfileInterpolation to Quadratic3.

Examples

ScanSingleEdge_Direct locates the strongest edge across inScanPath.

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.