fft_image — 2D `frequency` op

• Data kinds: image → image

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

• HALCON equivalent: fft_image (the HALCON reference is a useful guide to its meaning and parameters)

Usage

> This operator's description has not been translated yet. The original text follows as it is.

2 次元 FFT のパワースペクトルを `log1p(|F|)` で圧縮し正規化した画像。

低周波(直流)成分が中心にくるよう `fftshift` 済み。周期的なノイズや

テクスチャの空間周波数を可視化するのに使う。HALCON の `fft_image`

（Compute the fast Fourier transform of an image.）に相当。

`a, b` は未使用 ―― 画像全体に対するグローバルな FFT で、窓関数や

帯域選択のような調整点は無い。

Detailed usage guide

• gallery2d_texture_freq 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_texture_freq — py -3.11 examples/gallery2d_texture_freq.py

Ops the type connects to (they accept `image` as input)

identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter

Same category (`frequency`)

lowpass · highpass · sk_butterworth · power_real · power_byte · phase_rad · highpass_image · bandpass_image

*Provenance: ops.py — 2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

fft_image — 2D frequency op