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# ScanSingleEdge

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

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

C++
C#

void avl::ScanSingleEdge
(
const avl::Image& inImage,
const avl::ScanMap& inScanMap,
const avl::EdgeScanParams& inEdgeScanParams,
avl::Selection::Type inEdgeSelection,
atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
atl::Conditional<avl::Edge1D>& outEdge,
atl::Optional<avl::Profile&> outBrightnessProfile = atl::NIL,
atl::Optional<avl::Profile&> outResponseProfile = atl::NIL
)


### Parameters

Name Type Default Description
inImage const Image& Input image
inScanMap const ScanMap& Data precomputed with CreateScanMap
inEdgeScanParams const EdgeScanParams& EdgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f MinMagnitude: 5.0f EdgeTransition: BrightToDark ) Parameters controlling the edge extraction process
inEdgeSelection Selection::Type Selection::​Best 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
outBrightnessProfile Optional<Profile&> NIL Extracted image profile
outResponseProfile Optional<Profile&> NIL Profile 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: outBrightnessProfile, outResponseProfile.

### Description

The operation scans the image using inScanMap previously generated from a scan path 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.

### 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 locates the strongest edge using a scan map representing the scan path above.

### 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.