region op• Data kinds: region → region
• Call: fullseye.apply(img, "get_region_contour", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: get_region_contour (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):
▸ get_region_contour: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ get_region_contour: other inputs (docs site)
Extracts the contour (boundary, 1 pixel wide) of the region. Subtracts a single binary erosion of the region to leave the contour. For a region with holes it returns the hole boundaries as well, not only the outer one (measured 2026-09-16: on an 8x8 frame with a 4x4 hole, 16 of the 20 foreground pixels adjacent to the hole come out as contour). "region minus its erosion" leaves one pixel on the outside and on the hole side alike, so fill the holes first if you want the outer boundary only. a and b are unused. Same implementation as the `boundary` seed op.
> The detailed description below is the original text — the summary and the headings are translated.
HALCON の `get_region_contour`（領域の輪郭を取得する演算、本来は XLD 輪郭として座標列を返す）とは出力形式が異なる近似 —— この backend は輪郭を region（画素マスク）として返し、XLD の座標点列にはしていない。
• 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 get_region_contour 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_region — py -3.11 examples/gallery2d_region.py
• poc_document_scan — py -3.11 examples/poc_document_scan.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.