features op• Data kinds: region → feature
• Call: fullseye.apply(img, "rectangularity", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: rectangularity (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):
▸ rectangularity: stages (docs site)
Rectangularity. A rectangle with the same first and second order moments is constructed and the area of the difference to the region is normalised by the area of that rectangle (`1 - |region XOR rectangle| / |rectangle|); it is 1 for a rectangle. **The same definition as** HALCON's rectangularity` (Shape factor for the rectangularity of a region.).
> The detailed description below is the original text — the summary and the headings are translated.
★2026-09-26 まで軸平行の外接矩形との比(`skimage の extent`)だった。
向きを見ないので、同じ長方形を 30 度回しただけで 1.000 が 0.359 に落ちていた
(HALCON は 0.998 のまま)。`docs/hardening/halcon-named-shape-factors.md`。
★正方形や円のように 2 次モーメントで向きが決まらない形では、「同じモーメントを
持つ矩形」が向きの数だけ在って定義が向きを決めない。ここでは重なりが最大に
なる向きを選ぶ —— そのまま任意の向きで当てると正方形が 0.651 になり、HALCON の
「矩形なら 1」と食い違う。HALCON もこの形では最大 10% 過小評価すると明記する。
`a, b` は未使用。
• gallery2d_features 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 rectangularity 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_features — py -3.11 examples/gallery2d_features.py
• shape_factors_closed_form — py -3.11 examples/shape_factors_closed_form.py
feature as input)features)effective_bit_depth · blob_count · area_frac · count_contours · total_length · vol_count · sk_euler · sk_entropy_feat
*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.