segmentation op• Data kinds: image → region
• Call: fullseye.apply(img, "fast_threshold", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: fast_threshold (the HALCON reference is a useful guide to its meaning and parameters)
*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).*
Binarization with a fixed threshold. Pixels where `x falls within the band (a, a+0.5+0.5b) become the foreground (1) (sharing the fixed branch of _sh_threshold with the threshold` seed op). a sets the lower bound, and b sets the band width (upper bound).
> The detailed description below is the original text — the summary and the headings are translated.
HALCON の `fast_threshold`（大域しきい値による高速な二値化、通常は単純な閾値以上/以下の判定）に相当するが、この実装は下限・上限の両方を持つ帯域しきい値である点、および高速化のための整数近似などは行っていない点で近似。
• gallery2d_segmentation 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.
fast_threshold 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_segmentation — py -3.11 examples/gallery2d_segmentation.py
region as input)identity · reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small
segmentation)threshold · otsu · canny · adaptive_gauss_thresh · sk_otsu · sk_li · sk_yen · sk_sauvola
*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.