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ScanExactlyNRidges

Header:	AVL.h
Namespace:	avl
Module:	MetrologyBasic

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

Applications: Very fast detection (or presence verification) of thin structures like wires or scale marks.

Syntax

void avl::ScanExactlyNRidges
(
	const avl::Image& inImage,
	const ScanMap& inScanMap,
	const RidgeScanParams& inRidgeScanParams,
	int inRidgeCount,
	avl::Selection::Type inRidgeSelection,
	float inMinDistance,
	atl::Optional<float> inMaxDistance,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	atl::Conditional<atl::Array<avl::Ridge1D> >& outRidges,
	atl::Conditional<atl::Array<avl::Gap1D> >& outGaps,
	atl::Optional<avl::Profile&> outBrightnessProfile = atl::NIL,
	atl::Optional<avl::Profile&> outResponseProfile = atl::NIL
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Input image
inScanMap	const ScanMap&			Data precomputed with CreateScanMap
inRidgeScanParams	const RidgeScanParams&		RidgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f RidgeWidth: 5 RidgeMargin: 2 MinMagnitude: 5.0f RidgePolarity: Dark )	Parameters controlling the ridge extraction process
inRidgeCount	int	0 -	1	Number of ridges to be found
inRidgeSelection	Selection::Type		Selection::Best	Selection mode of the resulting ridges
inMinDistance	float	0.0 -	0.0f	Minimal distance between consecutive ridges
inMaxDistance	Optional<float>	0.0 -	NIL	Maximal distance between consecutive ridges
inLocalBlindness	Optional<const LocalBlindness&>		NIL	Defines conditions in which weaker ridges can be detected in the vicinity of stronger ridges
outRidges	Conditional<Array<Ridge1D> >&			Found ridges
outGaps	Conditional<Array<Gap1D> >&			Gaps between consecutive edges
outBrightnessProfile	Optional<Profile&>		NIL	Extracted image profile
outResponseProfile	Optional<Profile&>		NIL	Profile of the ridge 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 finds a set of inRidgeCount image ridges perpendicular to the path. If no subset (of inRidgeCount elements) of detected ridges meets the requirements of inRidgeScanParams.minMagnitude, inMinDistance, inRidgeScanParams.ridgePolarity then the outputs are set to NIL.

Note that in case of a scan path which is closed, the parameters controlling the distances between consecutive found objects do not control the distance between the first and the last of the found objects (counting from the beginning of the scan path).

Hints

Set inRidgeCount to the number of ridges that are to be found (the N number).
Define inEdgeScanParams.RidgePolarity to detect a particular ridge type, and only that type.
If the expected number of ridges cannot be found, try decreasing inRidgeScanParams.MinMagnitude. Verify this with the values on the outResponseProfile output.
If consecutive ridges are very close to each other, change inEdgeScanParams.ProfileInterpolation to Quadratic3.
Adjust inMinDistance (in pixels) to filter out false ridges that appear in proximity to other ridges.

Examples

ScanMultipleRidges locates the ridges 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.