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# ScanSingleEdge_Direct

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

C++
C#

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.