close_edgesclose_edgesCloseEdgesCloseEdgesclose_edges (Operator)

Name

close_edgesclose_edgesCloseEdgesCloseEdgesclose_edges — Close edge gaps using the edge amplitude image.

Signature

close_edges(Edges, EdgeImage : RegionResult : MinAmplitude : )

Description

close_edgesclose_edgesCloseEdgesCloseEdgesCloseEdgesclose_edges closes gaps in the output of an edge detector, and thus tries to produce complete object contours. This is done by examining the neighbors of each edge point to determine the point with maximum amplitude (i.e., maximum gradient), and adding the point to the edge if its amplitude is larger than the minimum amplitude passed in MinAmplitudeMinAmplitudeMinAmplitudeMinAmplitudeminAmplitudemin_amplitude. This operator expects as input the edges (EdgesEdgesEdgesEdgesedgesedges) and amplitude image (EdgeImageEdgeImageEdgeImageEdgeImageedgeImageedge_image) returned by typical edge operators, such as edges_imageedges_imageEdgesImageEdgesImageEdgesImageedges_image or sobel_ampsobel_ampSobelAmpSobelAmpSobelAmpsobel_amp. close_edgesclose_edgesCloseEdgesCloseEdgesCloseEdgesclose_edges does not take into account the edge directions that may be returned by an edge operator. Thus, in areas where the gradient is almost constant the edges may become rather “wiggly.”

Attention

Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.

Execution Information

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Automatically parallelized on tuple level.

Parameters

EdgesEdgesEdgesEdgesedgesedges (input_object) region(-array) → object

Region containing one pixel thick edges.

EdgeImageEdgeImageEdgeImageEdgeImageedgeImageedge_image (input_object) singlechannelimage → object (byte / uint2 / int4)

Edge amplitude (gradient) image.

RegionResultRegionResultRegionResultRegionResultregionResultregion_result (output_object) region(-array) → object

Region containing closed edges.

MinAmplitudeMinAmplitudeMinAmplitudeMinAmplitudeminAmplitudemin_amplitude (input_control) integer → (integer)

Minimum edge amplitude.

Default value: 16

Suggested values: 5, 8, 10, 12, 16, 20, 25, 30, 40, 50

Typical range of values: 1 ≤ MinAmplitude MinAmplitude MinAmplitude MinAmplitude minAmplitude min_amplitude ≤ 255

Minimum increment: 1

Recommended increment: 1

Restriction: MinAmplitude >= 0

Example (C)

sobel_amp(Image,&EdgeAmp,"sum_abs",5);
threshold(EdgeAmp,&EdgeRegion,40.0,255.0);
skeleton(EdgeRegion,&ThinEdge);
close_edges(ThinEdge,EdgeAmp,&CloseEdges,15);
skeleton(CloseEdges,&ThinCloseEdges);