features op• Data kinds: contour → feature
• Call: fullseye.apply(img, "area_center_xld", 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_xld (the HALCON reference is a useful guide to its meaning and parameters)
For the single contour with the largest number of points, computes the polygon area using the shoelace formula and returns it normalized by the total pixel count of the image. HALCON's `area_center_xld (Area and center of gravity (centroid) of contours and polygons.) is an operator that returns the centroid in addition to the area, but this stand-in returns only the area (the centroid information is lost in this approximation — a contractual constraint arising from the feature` sort being a single scalar).
> The detailed description below is the original text — the summary and the headings are translated.
`a, b` は未使用。輪郭が無ければ 0 を返す。
• 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 · area_frac · count_contours · total_length · vol_count · sk_euler · sk_entropy_feat · sk_blur_effect
*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.