region op• Data kinds: region → image
• Call: fullseye.apply(img, "xsp_chamfer_dist", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
*The figure is the real output on a synthetic 128×128 input. Left: input, right: output (a non-image return value is shown as the value itself).*
City-block (chamfer) distance to the nearest background pixel, normalised to [0,1].
> The detailed description below is the original text — the summary and the headings are translated.
★2026-09-02: 縮退入力での 符号つきセンチネル を潰す。
`scipy.ndimage.distance_transform_cdt` は「背景画素が 1 つも無い」入力に対して
距離ではなく -1 を全画素に書く(実測: `np.ones((8,8), bool)` -> min=max=-1)。
旧実装はそれをそのまま `_norm` に通していたので、**塗り潰された領域の距離マップが
一様 -1 の「画像」**になっていた —— 例外も警告も出ないまま値域 [0,1] の image 契約を
破り、保存・表示では全面が黒に潰れる。
背景が無い = どの画素も「無限に遠い」ので、正規化後の正直な答えは 一様 1.0。
前景が無いときは距離 0 の一様 0.0。どちらも符号つきの値を返さない。
• 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 xsp_chamfer_dist 0.50 0.50
▸ Load this pipeline · Load & run
• 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.