halcon_ext op• Data kinds: contour → feature
• Call: fullseye.apply(img, "hx_test_self_intersect", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: test_self_intersection_xld (the HALCON reference is a useful guide to its meaning and parameters)
*The figure is the actual output on a synthetic 128×128 input. Left: input, right: output. Point clouds are drawn as a top-down scatter (brightness = z), 1-D series as a line plot, volumes as the maximum-intensity projection along z, videos as the middle frame, complex images as magnitude; return values that are not pictures are shown as the values themselves.*
*Knob a does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
*Knob b does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
Stages (the ops that come before → this op, left to right):
▸ hx_test_self_intersect: stages (docs site)
The fraction of contours that self-intersect (a feature). Non-adjacent segment pairs are tested.
For each contour (4 or more points), tests all pairs of non-adjacent segments (i, i+1) and (j, j+1) (j >= i+2) for intersection by the sign of the oriented area (ccw test), and returns the fraction of contours with at least 1 intersecting pair over the total number of contours as np.float64. For a closed curve whose start and end coincide (distance below 1e-6), the pair of first and last segment is treated as adjacent and excluded.
• a, b are unused.
• 0.0 if there are no contours. Contours with 3 or fewer points count as non-intersecting.
Only proper crossings are detected; touching (an end point lying on the other segment) and collinear overlap are not (the inequalities are strict). The cost per contour grows with the 2nd power of the number of segments, so it is slow for contours with many points (reduce points first with hx_split_contours or smooth_contours_xld). Useful to detect breakdown of an outline shifted inward with hx_gen_parallel_contour.
• gallery2d_halcon_ext family guide
• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).
• Operator provenance and references — the sources of the research/methods this op family came from.
• The canonical algorithm (author, year) and its uses are named in the family usage guide above.
The program below has been verified to run (same input as the figure). In Studio's help this block becomes buttons that load and run it on the spot.
threshold 0.50 0.50 sk_find_contours 0.50 0.50 hx_test_self_intersect 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_halcon_ext — py -3.11 examples/gallery2d_halcon_ext.py
feature as input)halcon_ext)hx_gen_circle · hx_gen_ellipse · hx_gen_rectangle2 · hx_gen_checker_region · hx_gen_grid_region · hx_gabor · hx_fit_surface1 · hx_fit_surface2
*Provenance: ops.py — 2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.