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ScanExactlyNStripes

Locates a specified number of multiple pairs of opposite edges across 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
inStripeScanParams	StripeScanParams		Parameters controlling the stripe extraction process
inStripeCount	Integer	0 -	Number of stripes to be found
inStripeSelection	Selection		Selection mode of the resulting stripes
inMinGapWidth	Real	0.0 -	Minimal distance between consecutive stripes
inMaxGapWidth	Real *	0.0 -	Maximal distance between consecutive stripes
inLocalBlindness	LocalBlindness *		Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
outStripes	Stripe1D Array ?		Found stripes
outGaps	Gap1D Array ?		Gaps between consecutive stripes
outAlignedScanPath	Path		Path along which the scan is performed; in the image coordinate system
diagBrightnessProfile	Profile		Extracted image profile
diagResponseProfile	Profile		Profile of the edge (derivative) operator response
diagSamplingPoints	Path Array		Array of paths each one containing the sampling points that contributed to a single value of the extracted profile

Applications

Very fast detection (or presence verification) of multiple pairs of opposite edges.

Description

The operation scans the image along inScanPath and finds a set of inStripeCount consecutive stripes (i.e. pairs of opposite-polarity edges running across the path). If no subset (of inStripeCount elements) of detected edge pairs meets the requirements of inStripeScanParams.stripePolarity, inStripeScanParams.minMagnitude, inStripeScanParams.minStripeWidth and inMinGapWidth 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.

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

Connect an input image to the inImage input.
Set inStripeCount to the number of stripes that are to be found (the N number).
Create inScanPath which is more or less perpendicular to the stripes you want to detect. It should be long enough to anticipate all possible stripe locations.
Define inStripeScanParams.StripePolarity to detect a particular stripe 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 inStripeScanParams.SmoothingStdDev.
If the expected number of stripes cannot be found, try decreasing inStripeScanParams.MinMagnitude. Verify this with the values on the diagResponseProfile output.
If consecutive edges are closer than 6 pixels apart, change inStripeScanParams.ProfileInterpolation to Quadratic3.
Adjust inMinGapWidth (in pixels) to filter out false stripes that appear in proximity to other stripes.
Adjust inStripeScanParams.inMinStripeWidth and inStripeScanParams.inMaxStripeWidth (in pixels) to increase reliability.

Examples

Description of usage of this filter can be found in examples and tutorial: Meter.

ScanExactlyNStripes locates the edge pairs across inScanPath (inStripeCount = 2, inStripeScanParams.stripePolarity = Dark).

Remarks

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 filters is member of ScanStripes filter group.