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)
*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).*
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.
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 area_frac 0.50 0.50
▸ Load this pipeline · Load & run
• 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.