contour op• Data kinds: region → contour
• Call: fullseye.apply(img, "gen_contour_region_xld", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: gen_contour_region_xld (the HALCON reference is a useful guide to its meaning and parameters)
Extracts the outer boundary of a region (pixel mask) as an XLD contour, preserving trace order (order along the boundary). Uses `find_contours` (subpixel contours via marching squares) if skimage is available, otherwise falls back to a custom Moore-neighborhood tracing (8-neighborhood, Jacob's stopping criterion). a and b are unused.
> The detailed description below is the original text — the summary and the headings are translated.
2026-08-30 の修正で、以前使っていた汎用の `edges_sub_pix 経路は np.where のラスタ順で点を返しており、順序に依存する後段処理（楕円フーリエ記述子など）を壊していた。HALCON の gen_contour_region_xld`（region から XLD 輪郭を生成する演算）に相当する。
• gallery2d_contour_measure 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_contour_measure — py -3.11 examples/gallery2d_contour_measure.py
contour as input)identity · select_contours · smooth_contours · fit_line_contours · contours_to_region · count_contours · total_length · select_contours_xld
contour)select_contours · smooth_contours · fit_line_contours · contours_to_region · sk_find_contours · edges_sub_pix · lines_gauss · select_contours_xld
*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.