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Header: FIL.h
Namespace: fil
Module: MetrologyBasic

Locates the strongest dark or bright pixel peak along a given path.

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


void fil::ScanSingleRidge
	const fil::Image& inImage,
	const ScanMap& inScanMap,
	const RidgeScanParams& inRidgeScanParams,
	fil::Selection::Type inRidgeSelection,
	ftl::Optional<const fil::LocalBlindness&> inLocalBlindness,
	ftl::Conditional<fil::Ridge1D>& outRidge,
	ftl::Optional<fil::Profile&> outBrightnessProfile = ftl::NIL,
	ftl::Optional<fil::Profile&> outResponseProfile = ftl::NIL


Name Type Default Description
Input value inImage const Image& Input image
Input value inScanMap const ScanMap& Data precomputed with CreateScanMap
Input value inRidgeScanParams const RidgeScanParams& RidgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f RidgeWidth: 5 RidgeMargin: 2 MinMagnitude: 5.0f RidgePolarity: Dark ) Parameters controlling the ridge extraction process
Input value inRidgeSelection Selection::Type Selection::​Best Selection mode of the resulting ridge
Input value inLocalBlindness Optional<const LocalBlindness&> NIL Defines conditions in which weaker ridges can be detected in the vicinity of stronger ridges
Output value outRidge Conditional<Ridge1D>& Found ridge
Output value outBrightnessProfile Optional<Profile&> NIL Extracted image profile
Output value outResponseProfile Optional<Profile&> NIL Profile of the ridge operator response

Optional Outputs

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

Read more about Optional Outputs.


The operation scans the image using inScanMap previously generated from a scan path and locates the strongest ridge of the given characteristics. If there is no such ridge then the outputs are set to NIL.


  • 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 locates the strongest ridge using a scan map representing the scan path above.


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 – Locates a specified number of the strongest dark or bright pixel peak along a given path.
  • ScanSingleRidge_Direct – Locates the strongest dark or bright pixel peak along a given path (without a scan map).