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ScanExactlyNStripes
Locates a specified number of multiple pairs of opposite edges across a given path.
Syntax
void avl::ScanExactlyNStripes ( const avl::Image& inImage, const ScanMap& inScanMap, const StripeScanParams& inStripeScanParams, int inStripeCount, avl::Selection::Type inStripeSelection, float inMinGapWidth, atl::Optional<float> inMaxGapWidth, atl::Optional<const avl::LocalBlindness&> inLocalBlindness, atl::Conditional<atl::Array<avl::Stripe1D> >& outStripes, atl::Conditional<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 | ||
|
inStripeCount | int | 0 -  |
1 | Number of stripes to be found |
|
inStripeSelection | Selection::Type | Selection::Best | Selection mode of the resulting stripes | |
|
inMinGapWidth | float | 0.0 - |
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 | Conditional<Array<Stripe1D> >& | Found stripes | ||
|
outGaps | Conditional<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 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.
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
- Set inStripeCount to the number of stripes that are to be found (the N number).
- Define inStripeScanParams.StripePolarity to detect a particular stripe type, and only that type.
- 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
ScanExactlyNStripes locates the edge pairs using a scan map representing the scan path above (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.
