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FitPathToRidges

Basic

Module: MetrologyPro

Performs a series of 1D ridge detections and creates a path from the detected points.

Applications

Tracing of a thin line, whose rough location and shape is known beforehand.
Name Type Range Description
Input value inImage Image Image to fit the path to
Input value inFittingField PathFittingField Path fitting field
Input value inFittingFieldAlignment CoordinateSystem2D* Adjusts the fitting field to the position of the inspected object
Input value inScanStep Real* 0.0 - Optional implicit conversion of the input path to an equidistant one
Input value inScanWidth Integer 1 - The width of each scan field (in pixels)
Input value inSamplingParams SamplingParams Parameters controlling the sampling process
Input value inRidgeScanParams RidgeScanParams Parameters controlling the ridge extraction process
Input value inRidgeSelection Selection Selection mode of ridges
Input value inLocalBlindness LocalBlindness* Defines conditions in which weaker ridges can be detected in the vicinity of stronger ridges
Input value inMaxInterpolationLength Integer* 0 - Maximal number of consecutive points not found
Input value inMaxDeviationDelta Real* 0.0 - Maximal difference between deviations of consecutive path points
Input value inMaxIncompleteness Real 0.0 - 0.999 Maximal fraction of ridge points not found
Output value outPath Path? Fitted path or nothing if the fitting failed
Output value outRidges Ridge1D?Array Found ridges
Output value outDeviationProfile Profile? Profile of distances between the actual path points and the corresponding reference path points
Output value outAlignedFittingField PathFittingField Fitting field used; in the image coordinate system
Output value outBrightnessProfiles ProfileArray Extracted image profiles
Output value outResponseProfiles ProfileArray Profiles of the ridge operator response
Diagnostic input diagScanSegments Segment2DArray Segments along which the scans were run
Diagnostic input diagSamplingAreas Rectangle2DArray Areas from which the input image is sampled

Description

The operation tries to fit a given path to ridges present in the inImage image. Internally, it performs a series of scans with the ScanSingleRidge filter along a number of specific scan segments which length is always equal to the inFittingField width and cannot be less than 4. The found points are then used to determine the actual position of the path in the image. Only inMaxIncompleteness fraction of these scans may fail. If the fitting according to the given parameters is not possible, outPath is set to Nil.

There are also another parameters that control the path fitting process. The inMaxDeviationDelta parameter defines the maximal allowed difference between deviations of consecutive points from the input path points. If some of the scans fail or if some of found points are classified to be wrong according to another control parameters, output path points corresponding to them are interpolated depending on points in their nearest vicinity. No more than inMaxInterpolationLength consecutive points can be interpolated. The exception to this behavior are points which were not found on both ends of the input path. Those are not part of the result at all.

Hints

  • Connect an input image to the inImage input.
  • If the object location is variable, connect inFittingFieldAlignment to an appropriate local coordinate system (e.g. from a template matching filter).
  • Define the inFittingField input to specify the area in which ridge scanning will be performed.
  • Define inRidgeScanParams.RidgePolarity to detect a particular ridge type, and only that type.
  • Adjust inRidgeScanParams.RidgeWidth to the expected thickness of the ridge (in pixels).
  • If the noise level is high, try increasing inScanWidth and/or inRidgeScanParams.SmoothingStdDev.
  • If no or too few ridge points are found, try decreasing inRidgeScanParams.MinMagnitude.
  • If some of the scans may fail, set the inMaxIncompleteness input accordingly.
  • Use the diagScanSegments and outRidges outputs to visualize the scanning results.

Examples

Fitting a path to the walls of a plastic capsule
(inRidgeScanParams.RidgePolarity = Dark, inRidgeScanParams.RidgeWidth = 6, inRidgeScanParams.RidgeOperator = ArithmeticMean).

Remarks

Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.

This filter is a part of the Shape Fitting toolset. To read more about this technique, one can refer to the Shape Fitting chapter of our Machine Vision Guide

Hardware Acceleration

This operation supports automatic parallelization for multicore and multiprocessor systems.

Complexity Level

This filter is available on Basic Complexity Level.

Filter Group

This filter is member of FitPath filter group.

See Also

  • FitPathToEdges – Performs a series of 1D edge detections and creates a path from the detected points.
  • FitPathToStripe – Performs a series of 1D stripe detections and creates a path from the detected points.