fft_generic — 2D frequency op

• Data kinds: image → image

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

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

Usage

Returns the log-compressed amplitude spectrum of the image's Fourier transform (`log1p(|F|) normalized by its maximum). The center corresponds to low-frequency components and the periphery to high-frequency components (already fftshift`-ed). a and b are unused.

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

HALCON の `fft_generic（順変換・逆変換・実数/複素数など多数のモードを持つ汎用 FFT 演算）のうち、順方向の振幅スペクトル表示だけを実装した近似 —— 逆変換や位相成分などの他モードは別 op（fft_image_inv、phase_deg` など）が個別に担う。

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 · 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.