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Locates multiple dark or bright pixel peaks along a given path.

Name Type Range Description
inImage Image Input image to be measured
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
inMinDistance Real 0.0 - Minimal distance between consecutive ridges
inMaxDistance Real* 0.0 - Maximal distance between consecutive ridges
inLocalBlindness LocalBlindness* Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
outRidges Ridge1DArray Found ridges
outGaps Gap1DArray Gaps between consecutive ridges
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 multiple thin structures like scratches or scale marks - usually for counting or distance measurements.


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 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).


  • 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.
  • 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 too few ridges are found, try decreasing inRidgeScanParams.MinMagnitude. Verify this with the values on the diagResponseProfile 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.


ScanMultipleRidges locates the ridges 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.
  • ScanSingleRidge – Locates the strongest dark or bright pixel peak along a given path.