Locates multiple transitions between dark and bright pixels along a given path.
Applications: Very fast detection of multiple edge points - usually for object counting or displacement detection.
void avl::ScanMultipleEdges ( const avl::Image& inImage, const ScanMap& inScanMap, const EdgeScanParams& inEdgeScanParams, float inMinDistance, atl::Optional<float> inMaxDistance, atl::Optional<const avl::LocalBlindness&> inLocalBlindness, atl::Array<avl::Edge1D>& outEdges, atl::Array<avl::Gap1D>& outGaps, avl::Profile& diagBrightnessProfile, avl::Profile& diagResponseProfile )
|inImage||const Image&||Input image|
|inScanMap||const ScanMap&||Data precomputed with CreateScanMap|
|inEdgeScanParams||const EdgeScanParams&||EdgeScanParams ( ProfileInterpolation: Quadratic4 SmoothingStdDev: 0.6f MinMagnitude: 5.0f EdgeTransition: BrightToDark )||Parameters controlling the edge extraction process|
|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|
|outGaps||Array<Gap1D>&||Gaps between consecutive edges|
|diagBrightnessProfile||Profile&||Extracted image profile|
|diagResponseProfile||Profile&||Profile of the edge (derivative) operator response|
The operation scans the image using inScanMap previously generated from a scan path and detects image edges perpendicular to the path. Depending on the inEdgeScanParams.edgeTransition parameter, edges representing increase or decrease (or both) of image brightness along the path will be taken into account.
When the number of edges to be found is known, one can use the ScanExactlyNEdges.
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).
- Define inEdgeScanParams.EdgeTransition to detect a particular edge type, and only that type.
- If too few edges are 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.
Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.
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.
- CreateScanMap – Precomputes a data object that is required for fast 1D edge detection.
- ScanSingleEdge – Locates the strongest transition between dark and bright pixels along a given path.
- ScanExactlyNEdges – Locates a specified number of the strongest transitions between dark and bright pixels along a given path.
- ScanExactlyNEdges_Direct – Locates a specified number of the strongest transitions between dark and bright pixels along a given path (without a scan map).