region op• Data kinds: region → region
• Call: fullseye.apply(img, "r2_smallest_rectangle2", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: smallest_rectangle2 (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):
▸ r2_smallest_rectangle2: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ r2_smallest_rectangle2: other inputs (docs site)
Minimum-area ORIENTED bounding rectangle as a mask (rotating calipers).
> The detailed description below is the original text — the summary and the headings are translated.
領域の全前景画素を含む最小面積の回転矩形をマスクとして描く。前景座標の凸包を
取り、凸包の各辺に平行な向きで外接矩形を作って面積最小のものを選ぶ
(rotating calipers。最小面積矩形は凸包のいずれかの辺に接するという性質を使う)。
内部表現は中心 `(cy, cx)、長辺 long_len、短辺 short_len`、長辺の向き
`angle`(画像座標 x=col, y=row で測ったラジアン)。
`a は長辺だけを 1 + 0.3*a 倍に伸ばす(a=0` で最小矩形そのもの、
`a=1 で長辺 1.3 倍。短辺は変えない)。b` は未使用。描画は中心からの
射影 `|pu| <= long/2 + 0.5、|pv| <= short/2 + 0.5` で、画素の広がりぶん
0.5 画素の余白を足すため出力は入力領域を必ず含む。
返り値は入力と同形の float64 0/1 マスク、前景が無ければ全零。角度や辺長の
数値は返さない。複数の連結成分があれば全体で 1 つの矩形。前景が 1 画素や
一直線上の場合は退化(点・線分)し、描画は 1 画素幅程度の細い帯になる。
軸並行でよければ `r2_smallest_rectangle1` の方が軽い。細長い部品の向きを
見る前処理や、`r2_inner_rectangle1` との面積比で矩形らしさを見る用途に。
Border handling: treat everything outside the image as background (0) (measured; tools/impl2/border_probe.py).
• gallery2d_region 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 r2_smallest_rectangle2 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_region — py -3.11 examples/gallery2d_region.py
region as input)identity · reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small
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).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.