halcon_ext op• Data kinds: contour → contour
• Call: fullseye.apply(img, "hx_crop_contours", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: crop_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_crop_contours: knob a sweep (docs site)
Sweeping knob b (0.1 / 0.5 / 0.9, the other knob at its default):
▸ hx_crop_contours: knob b sweep (docs site)
Stages (the ops that come before → this op, left to right):
▸ hx_crop_contours: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ hx_crop_contours: other inputs (docs site)
Crop contours to the central a×b fraction rectangle (keeping only the points inside).
Of each contour's points, keeps only those within hh in the row direction and within ww in the column direction of the image centre (H/2, W/2), discards contours with not even 1 point left, and returns the rest.
• a → half of the kept height hh = (0.3 + 0.6*a) * H/2 (30% to 90% of the whole).
• b → half of the kept width ww = (0.3 + 0.6*b) * W/2 (30% to 90% of the whole). Even at a=b=1 the outer 5% is dropped.
It only thins out points without splitting, so a contour that leaves the rectangle and comes back has its remaining points joined (a jump). To ignore everything outside the rectangle completely, apply hx_split_contours downstream. The version that specifies margins from the image border is hx_clip_contours; the version with 1 knob for a square window is xg_crop_contours.
• 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_crop_contours 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_halcon_ext — py -3.11 examples/gallery2d_halcon_ext.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.