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AvsFilter_ScanExactlyNEdges
This is Filter Equivalent. This function may be present in generated code, but should not be used in hand-written code. CreateScanMap and ScanExactlyNEdges should be used instead.
Locates a specified number of the strongest transitions between dark and bright pixels along a given path.
Header: | AVL.h |
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Syntax
void avs::AvsFilter_ScanExactlyNEdges ( ScanExactlyNEdgesState& ioState, const avl::Image& inImage, const avl::Path& inScanPath, atl::Optional<const avl::CoordinateSystem2D&> inScanPathAlignment, int inScanWidth, avl::InterpolationMethod::Type inImageInterpolation, const avl::EdgeScanParams& inEdgeScanParams, int inEdgeCount, avl::Selection::Type inEdgeSelection, float inMinDistance, atl::Optional<float> inMaxDistance, atl::Optional<const avl::LocalBlindness&> inLocalBlindness, atl::Conditional<atl::Array<avl::Edge1D> >& outEdges, atl::Conditional<atl::Array<avl::Gap1D> >& outGaps, atl::Optional<avl::Path&> outAlignedScanPath = atl::NIL, avl::Profile& diagBrightnessProfile, avl::Profile& diagResponseProfile, atl::Array<avl::Path>& diagSamplingPoints )
Parameters
Name | Type | Range | Default | Description | |
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ioState | ScanExactlyNEdgesState& | Object used to maintain state of the function. | |||
inImage | const Image& | Input image to be measured | |||
inScanPath | const Path& | Path along which the scan is performed | |||
inScanPathAlignment | Optional<const CoordinateSystem2D&> | NIL | Adjusts the scan path to the position of the inspected object | ||
inScanWidth | int | 1 - | 5 | Width of the scan field in pixels | |
inImageInterpolation | InterpolationMethod::Type | Bilinear | Interpolation method used in extraction of image pixel values | ||
inEdgeScanParams | const EdgeScanParams& | EdgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f MinMagnitude: 5.0f EdgeTransition: BrightToDark ) | Parameters controlling the edge extraction process | ||
inEdgeCount | int | 0 - | 1 | Number of edges to be found | |
inEdgeSelection | Selection::Type | Selection mode of the resulting edges | |||
inMinDistance | float | 0.0 - | 0.0f | Minimal distance between consecutive edges | |
inMaxDistance | Optional<float> | 0.0 - | NIL | Maximal distance between consecutive edges | |
inLocalBlindness | Optional<const LocalBlindness&> | NIL | Defines conditions in which weaker edges can be detected in the vicinity of stronger edges | ||
outEdges | Conditional<Array<Edge1D> >& | Found edges | |||
outGaps | Conditional<Array<Gap1D> >& | Gaps between consecutive edges | |||
outAlignedScanPath | Optional<Path&> | NIL | 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 | Array<Path>& | Array of paths each one containing the sampling points that contributed to a single value of the extracted profile |
Description
The operation scans the image along inScanPath and finds a set of inEdgeCount image edges perpendicular to the path. If no subset (of inEdgeCount elements) of detected edges meets the requirements of inEdgeScanParams.minMagnitude, inMinDistance, inEdgeScanParams.edgeTransition 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
- Set inEdgeCount to the number of edges that are to be found (the N number).
- Define inEdgeScanParams.EdgeTransition to detect a particular edge type, and only that type.
- If the expected number of edges cannot be found, try decreasing inEdgeScanParams.MinMagnitude. Verify this with the values on the diagResponseProfile output.
- If consecutive edges are closer than 6 pixels apart, change inEdgeScanParams.ProfileInterpolation to Quadratic3.
- Adjust inMinDistance (in pixels) to filter out false edges that appear in proximity to other edges.
Examples
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
- AvsFilter_ScanExactlyNEdges – Locates a specified number of the strongest transitions between dark and bright pixels along a given path.
- AvsFilter_ScanSingleEdge – Locates the strongest transition between dark and bright pixels along a given path.
- CreateScanMap – Precomputes a data object that is required for fast 1D edge detection.