| Operators |
close_edges_length — Close edge gaps using the edge amplitude image.
close_edges_length(Edges, Gradient : ClosedEdges : MinAmplitude, MaxGapLength : )
close_edges_length closes gaps in the output of an edge detector, and thus tries to produce complete object contours. This operator expects as input the edges (Edges) and amplitude image (Gradient) returned by typical edge operators, such as edges_image or sobel_amp.
Contours are closed in two steps: First, one pixel wide gaps in the input contours are closed, and isolated points are eliminated. After this, open contours are extended by up to MaxGapLength points by adding edge points until either the contour is closed or no more significant edge points can be found. A gradient is regarded as significant if it is larger than MinAmplitude. The neighboring points examined as possible new edge points are the point in the direction of the contour and its two adjacent points in an 8-neighborhood. For each of these points, the sum of its gradient and the maximum gradient of that points three possible neighbors is calculated (look ahead of length 1). The point with the maximum sum is then chosen as the new edge point.
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.
Region containing one pixel thick edges.
Edge amplitude (gradient) image.
Region containing closed edges.
Minimum edge amplitude.
Default value: 16
Suggested values: 5, 8, 10, 12, 16, 20, 25, 30, 40, 50
Typical range of values: 1 ≤ MinAmplitude ≤ 255
Minimum increment: 1
Recommended increment: 1
Restriction: MinAmplitude >= 0
Maximal number of points by which edges are extended.
Default value: 3
Suggested values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 30, 40, 50, 70, 100
Typical range of values: 1 ≤ MaxGapLength ≤ 127
Minimum increment: 1
Recommended increment: 1
Restriction: MaxGapLength > 0 && MaxGapLength <= 127
sobel_amp(Image,&EdgeAmp,"sum_abs",5); threshold(EdgeAmp,&EdgeRegion,40.0,255.0); skeleton(EdgeRegion,&ThinEdge); close_edges_length(ThinEdge,EdgeAmp,&CloseEdges,15,3);
close_edges_length returns 2 (H_MSG_TRUE) if all parameters are correct. If the input is empty the behavior can be set via set_system('no_object_result',<Result>). If necessary, an exception is raised.
edges_image, sobel_amp, threshold, skeleton
close_edges, dilation1, closing
M. Üsbeck: “Untersuchungen zur echtzeitfähigen Segmentierung”; Studienarbeit, Bayerisches Forschungszentrum für Wissensbasierte Systeme (FORWISS), Erlangen, 1993.
Foundation
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