features op• Data kinds: region → feature
• Call: fullseye.apply(img, "area_frac", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: area_center (the HALCON reference is a useful guide to its meaning and parameters)
A feature that returns the fraction of pixels occupied by a region (area ratio). Unlike HALCON's `area_center` (Area and center of regions.), it returns only the area and does not compute the centroid (it corresponds to only part of that function).
> The detailed description below is the original text — the summary and the headings are translated.
`a, b は未使用。v > 0.5 で二値化した画素の平均値（= 前景画素数 / 全画素数）をスカラーで返す。値域は [0,1]`。
• gallery2d_features 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_features — py -3.11 examples/gallery2d_features.py
feature as input)features)blob_count · count_contours · total_length · vol_count · sk_euler · sk_entropy_feat · sk_blur_effect · cv_cc_count
*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.