region op• Data kinds: region → image
• Call: fullseye.apply(img, "cv_dist", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: distance_transform (the HALCON reference is a useful guide to its meaning and parameters)
Distance transform (OpenCV implementation, L2/Euclidean approximation). For each pixel in the foreground region, computes the distance to the nearest background pixel and returns it as an image - used as preprocessing for extracting a region's "thickness" or its centerline.
> The detailed description below is the original text — the summary and the headings are translated.
HALCON の distance_transform(Compute the distance transformation of a region.)に相当。実装は `cv2.distanceTransform(_u8(binm(v)), DIST_L2, maskSize=3)` を正規化したもの(cv2 は float32 で返すが、契約に合わせて float64 化 —— 2026-09-03 実測でベンチマーク済み)。maskSize=3 は 3x3 近傍での近似計算(厳密なユークリッド距離ではなく高速近似)。a, b は未使用。
• 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.
• gallery2d_region — py -3.11 examples/gallery2d_region.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
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.