xmh_pftas — 2D texture-feature op

• Data kinds: image → feature

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

Usage

Variance of the 54-dimensional PFTAS (parameter-free threshold adjacency statistics, `mahotas.features.pftas`) feature vector. A texture feature that aggregates histograms counting adjacent-pixel intensity relationships using a parameter-free threshold.

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

`a, b` は未使用。2026-09-02 実測: 54 次元の平均を使うと、正規化ヒストグラムの性質上ほぼ整数/54 の値しか取らず、12 通りの画像(4 サイズ x 3 内容)で相異なる値がわずか 2 個(事実上の定数)だった。分散にすると分布の広がりが残り画像ごとに変化するため、ここでは分散を採用している。

Detailed usage guide

• gallery2d_features 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_features — py -3.11 examples/gallery2d_features.py

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

identity

Same category (texture-feature)

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*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.