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

Name Type Range Description
inImage Image Input image
inScanPath Path Path along which the scan is performed
inScanPathAlignment CoordinateSystem2D* Adjusts the scan path to the position of the inspected object
inScanWidth Integer 1 - Width of the scan field in pixels
inImageInterpolation InterpolationMethod Interpolation method used in extraction of image pixel values
inRidgeScanParams RidgeScanParams Parameters controlling the ridge extraction process
inRidgeSelection Selection Selection mode of the resulting ridge
inLocalBlindness LocalBlindness* Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
outRidge Ridge1D? Found ridge
outAlignedScanPath Path Path along which the scan is performed; in the image coordinate system
diagBrightnessProfile Profile Extracted image profile
diagResponseProfile Profile Profile of the ridge operator response
diagSamplingPoints PathArray Array of paths each one containing the sampling points that contributed to a single value of the extracted profile
diagSamplingStep Real Used distance between consecutive sampling points on the scan path


Very fast detection of a thin structure like a scratch or a scale mark.


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.


  • Connect an input image to the inImage input.
  • Create inScanPath which is more or less perpendicular to the ridges you want to detect. It should be long enough to anticipate all possible ridge locations.
  • 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.
  • Use a local coordinate system connected to inScanPathAlignment to automatically adjust the measurement to variable object position (optional).
  • If the noise level is high, try increasing inScanWidth and/or inRidgeScanParams.SmoothingStdDev.
  • 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 across inScanPath.


For more information about local coordinate systems please refer to the following article.

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.

Complexity Level

This filter is available on Basic Complexity Level.

Filter Group

This filter is member of ScanRidges filter group.

See Also

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