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Header: AVL.h
Namespace: avl
Module: MetrologyBasic

Locates the strongest dark or bright pixel peak along a given path (without a scan map).

Applications: Very fast detection of a thin structure like a wire or a scale mark.


void avl::ScanSingleRidge_Direct
	const avl::Image& inImage,
	const avl::Path& inScanPath,
	atl::Optional<const avl::CoordinateSystem2D&> inScanPathAlignment,
	int inScanWidth,
	const avl::SamplingParams& inSamplingParams,
	const avl::RidgeScanParams& inRidgeScanParams,
	avl::Selection::Type inRidgeSelection,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	atl::Conditional<avl::Ridge1D>& outRidge,
	atl::Optional<avl::Path&> outAlignedScanPath = atl::NIL,
	avl::Profile& diagBrightnessProfile,
	avl::Profile& diagResponseProfile,
	atl::Array<avl::Path>& diagSamplingPoints,
	float& diagSamplingStep


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
inRidgeScanParams const RidgeScanParams& RidgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f RidgeWidth: 5 RidgeMargin: 2 MinMagnitude: 5.0f RidgePolarity: Dark ) Parameters controlling the ridge extraction process
inRidgeSelection Selection::Type Selection mode of the resulting ridge
inLocalBlindness Optional<const LocalBlindness&> NIL Defines conditions in which weaker ridges can be detected in the vicinity of stronger ridges
outRidge Conditional<Ridge1D>& Found ridge
outAlignedScanPath Optional<Path&> NIL Transformed input path
diagBrightnessProfile Profile& Extracted image profile
diagResponseProfile Profile& Profile of the ridge 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.

Read more about Optional Outputs.


The operation scans the image along inScanPath and locates the strongest ridge of the given characteristics. If there is no such ridge 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.


  • Adjust inRidgeScanParams.RidgeWidth to the expected thickness of the ridge (in pixels).
  • Define inRidgeScanParams.RidgePolarity to detect a particular ridge type, and only that type.
  • If no ridge is found, try decreasing inRidgeScanParams.MinMagnitude.
  • For difficult cases try different settings of the inRidgeScanParams.RidgeOperator parameter.


ScanSingleRidge_Direct locates the strongest ridge across inScanPath.


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.

See Also

  • CreateScanMap – Precomputes a data object that is required for fast 1D edge detection.
  • ScanExactlyNRidges_Direct – Locates a specified number of the strongest dark or bright pixel peak along a given path (without a scan map).
  • ScanSingleRidge – Locates the strongest dark or bright pixel peak along a given path.