threshold — 2D segmentation op

Data kinds: imageregion

Call: fullseye.apply(img, "threshold", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])

HALCON equivalent: threshold (the HALCON reference is a useful guide to its meaning and parameters)

Usage

Global thresholding. Equivalent to HALCON's `threshold` (Segment an image using global threshold.).

> The detailed description below is the original text — the summary and the headings are translated.

`a がしきい値そのもの(0〜1)で、v > a を満たす画素を前景(1)とする region を返す。b は未使用。HALCON の threshold` は下限・上限の 2 値を取れる帯域しきい値だが、この実装は下限のみの片側しきい値。

Detailed usage guide

gallery2d_segmentation 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.

Runnable examples (verified samples that actually call this op)

gallery2d_segmentationpy -3.11 examples/gallery2d_segmentation.py

video_streamingpy -3.11 examples/video_streaming.py

Ops the type connects to (they accept region as input)

identity · reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small

Same category (segmentation)

otsu · canny · adaptive_gauss_thresh · sk_otsu · sk_li · sk_yen · sk_sauvola · sk_niblack


*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.