gen_contour_region_xld — 2D `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)

gen_contour_region_xld: 入力 → 出力

*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).*

Usage

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。

Detailed usage guide

• gallery2d_contour_measure 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.

Try it in Studio

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
gen_contour_region_xld 0.50 0.50

▸ Load this pipeline · Load & run

Runnable examples (verified samples that actually call this op)

• gallery2d_contour_measure — py -3.11 examples/gallery2d_contour_measure.py

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

identity · select_contours · smooth_contours · fit_line_contours · contours_to_region · count_contours · total_length · select_contours_xld

Same category (`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).*

gen_contour_region_xld — 2D contour op