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ScanMultipleStripes


Locates multiple pairs of edges across a given path.

Header:AVL.h

Syntax

C++
C#
 
void avl::ScanMultipleStripes
(
	const avl::Image& inImage,
	const ScanMap& inScanMap,
	const StripeScanParams& inStripeScanParams,
	float inMinGapWidth,
	atl::Optional<float> inMaxGapWidth,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	atl::Array<avl::Stripe1D>& outStripes,
	atl::Array<avl::Gap1D>& outGaps,
	avl::Profile& diagBrightnessProfile,
	avl::Profile& diagResponseProfile
)

Parameters

Name Type Range Default Description
inImage const Image& Input image
inScanMap const ScanMap& Data precomputed with CreateScanMap
inStripeScanParams const StripeScanParams& Parameters controlling the stripe extraction process
inMinGapWidth float 0.0 - 0.0f Minimal distance between consecutive stripes
inMaxGapWidth Optional<float> 0.0 - NIL Maximal distance between consecutive stripes
inLocalBlindness Optional<const LocalBlindness&> NIL Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
outStripes Array<Stripe1D>& Found stripes
outGaps Array<Gap1D>& Distances between consecutive stripes
diagBrightnessProfile Profile& Extracted image profile
diagResponseProfile Profile& Profile of the edge (derivative) operator response

Description

The operation scans the image using inScanMap previously generated from a scan path and detects consecutive stripes (i.e. pairs of opposite-polarity edges running across the path). Depending on the inStripeScanParams.stripePolarity parameter, dark or bright stripes will be taken into account.

When the number of edge pairs to be measured is known, one can use the ScanExactlyNStripes filter.

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 inStripeScanParams.StripePolarity to detect a particular edge type, and only that type.
  • If too few stripes are 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 edges.
  • Adjust inStripeScanParams.inMinStripeWidth and inStripeScanParams.inMaxStripeWidth (in pixels) to increase reliability.

Examples

ScanMultipleStripes locates the edge pairs using a scan map representing the scan path above (inStripeScanParams.stripePolarity = Dark, inStripeScanParams.minStripeWidth = 45).

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.

See Also

  • CreateScanMap – Precomputes a data object that is required for fast 1D edge detection.
  • ScanExactlyNStripes – Locates a specified number of multiple pairs of opposite edges across a given path.