frequency op• Data kinds: image → image
• Call: fullseye.apply(img, "power_ln", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: power_ln (the HALCON reference is a useful guide to its meaning and parameters)
A stand-in for the power spectrum of a complex image. The implementation is identical to fft_generic: it applies its own FFT to the input image and returns the log of the amplitude, `log1p(|F|), normalized by its maximum (sharing the fft_power branch of _sh_freq`). a and b are unused.
> The detailed description below is the original text — the summary and the headings are translated.
HALCON の `power_ln`（複素画像のパワースペクトルを返す演算、通常は fft_generic 等が出力した複素画像を入力に取る）とは異なり、この実装は複素入力を受け取らず実画像から自前で FFT を計算する簡略近似。fft_generic とは実装上区別がない。
• gallery2d_texture_freq 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_texture_freq — py -3.11 examples/gallery2d_texture_freq.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
frequency)lowpass · highpass · sk_butterworth · fft_image · power_real · power_byte · phase_rad · highpass_image
*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.