halcon_ext op• Data kinds: contour → contour
• Call: fullseye.apply(img, "hx_split_contours", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: split_contours_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.*
Sweeping knob a (0.1 / 0.5 / 0.9, the other knob at its default):
▸ hx_split_contours: knob a sweep (docs site)
*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_split_contours: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ hx_split_contours: other inputs (docs site)
Split each contour into segments at its dominant points (RDP; the tolerance eps comes from a).
Applies Ramer-Douglas-Peucker to each contour (3 or more points) to find the indices of the dominant points, and lists each sub-sequence between neighbouring dominant points c[s:e+1] as a new contour (neighbouring segments share their end points). Contours with 2 or fewer points pass through unchanged.
• a → tolerance eps = 0.5 + a*5 (0.5 to 5.5 pixels). Bends within this distance are ignored, so a larger value gives segments that are
longer and fewer.
• b is unused.
The output is "one contour per segment", not just the polyline vertices (all original points remain). A closed contour (start = end) is first split at the point farthest from the start. The number of segments approximates the number of corners; placing hx_regress_contours downstream measures the straightness of each segment.
• 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_split_contours 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_halcon_ext — py -3.11 examples/gallery2d_halcon_ext.py
• poc_screw_thread_metrology — py -3.11 examples/poc_screw_thread_metrology.py
contour as input)identity · select_contours · smooth_contours · fit_line_contours · contours_to_region · count_contours · total_length · select_contours_xld
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.