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ScanMultipleRidges_Direct

Header:	FIL.h
Namespace:	fil
Module:	MetrologyBasic

Locates multiple dark or bright pixel peaks along a given path (without a scan map).

Applications: Very fast detection of multiple thin structures like wires or scale marks - usually for counting or distance measurements.

Syntax

void fil::ScanMultipleRidges_Direct
(
	const fil::Image& inImage,
	const fil::Path& inScanPath,
	ftl::Optional<const fil::CoordinateSystem2D&> inScanPathAlignment,
	int inScanWidth,
	const fil::SamplingParams& inSamplingParams,
	const fil::RidgeScanParams& inRidgeScanParams,
	float inMinDistance,
	ftl::Optional<float> inMaxDistance,
	ftl::Optional<const fil::LocalBlindness&> inLocalBlindness,
	ftl::Array<fil::Ridge1D>& outRidges,
	ftl::Array<fil::Gap1D>& outGaps,
	ftl::Optional<fil::Path&> outAlignedScanPath = ftl::NIL,
	ftl::Optional<fil::Profile&> outBrightnessProfile = ftl::NIL,
	ftl::Optional<fil::Profile&> outResponseProfile = ftl::NIL,
	ftl::Array<fil::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
inRidgeScanParams	const RidgeScanParams&		RidgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f RidgeWidth: 5 RidgeMargin: 2 MinMagnitude: 5.0f RidgePolarity: Dark )	Parameters controlling the ridge extraction process
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	Array<Ridge1D>&			Found ridges
outGaps	Array<Gap1D>&			Gaps between consecutive ridges
outAlignedScanPath	Optional<Path&>		NIL	Transformed input path
outBrightnessProfile	Optional<Profile&>		NIL	Extracted image profile
outResponseProfile	Optional<Profile&>		NIL	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 ftl::NIL to these parameters: outAlignedScanPath, outBrightnessProfile, outResponseProfile.

Description

The operation scans the image along inScanPath and detects ridges. Depending on the inRidgeScanParams.ridgePolarity parameter, dark, bright or both ridges will be taken into account.

When the number of ridges to be measured is known, one can use the ScanExactlyNRidges_Direct filter.

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.

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

Define inRidgeScanParams.RidgePolarity to detect a particular ridge type, and only that type.
If too few ridges are found, try decreasing inRidgeScanParams.MinMagnitude. Verify this with the values on the outResponseProfile output.
If consecutive ridges are very close to each other, change inRidgeScanParams.ProfileInterpolation to Quadratic3.
Adjust inMinDistance (in pixels) to filter out false ridges that appear in proximity to other ridges.

Examples

ScanMultipleRidges_Direct locates the ridges 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.