r3_region_features — 2D `region` op

• Data kinds: region → feature

• Call: fullseye.apply(img, "r3_region_features", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])

• HALCON equivalent: region_features (the HALCON reference is a useful guide to its meaning and parameters)

Usage

Returns one shape feature of the region (implements part of HALCON `region_features`).

> The detailed description below is the original text — the summary and the headings are translated.

`a < 0.5 なら正規化面積（前景画素数/全画素数）、a >= 0.5 なら真円度の逆数にあたるコンパクトネス P^2 / (4*pi*A)（P は 4 連結境界の周囲長。円で 1、正方形で約 1.27、細長いほど大きくなる）を返す。b` は未使用。領域が空なら 0.0。

Detailed usage guide

• gallery2d_region family guide

References (sample data, literature)

• 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.

Runnable examples (verified samples that actually call this op)

• gallery2d_region — py -3.11 examples/gallery2d_region.py

Ops the type connects to (they accept `feature` as input)

identity

Same category (`region`)

reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small · invert_region

*Provenance: ops.py — 2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

r3_region_features — 2D region op