sk_butterworth — 2D `frequency` op

• Data kinds: image → image

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

Usage

Butterworth filter (frequency domain). Applies an FFT to the image and acts as a high-pass filter that passes only components above a specified cutoff frequency (called with the default `high_pass=True`). Emphasizes high-frequency components of contours and texture.

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

HALCON に直接対応するものは無い(空欄)。実装は `filters.butterworth(v, cutoff_frequency_ratio=0.05+0.3*a) を [0,1]` に clip しただけ —— a はカットオフ比を 0.05〜0.35 に振る(小さいほど低周波まで削られ、応答が強く/広く出る)。b は未使用。ハイパスなので低コントラストな平坦領域は 0 付近に落ち、直流成分(平均輝度)の情報は失われる。

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 · fft_image · 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).*

sk_butterworth — 2D frequency op