frequency op• Data kinds: image → image
• Call: fullseye.apply(img, "highpass", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: highpass_image (the HALCON reference is a useful guide to its meaning and parameters)
High-pass filter via FFT (extracting contours and high-frequency components). Equivalent to HALCON's `highpass_image` (Extract high frequency components from an image.).
> The detailed description below is the original text — the summary and the headings are translated.
`a が遮断周波数 cutoff = 0.02 + 0.3a を振る。b は未使用。2-D FFT で rad > cutoff の高周波成分だけを残し、逆 FFT の実部を _signed01 で [0,1]` へ写す（0.5 が「変化なし」、それより明暗が高周波成分の符号を表す）。低域フィルタ同様、境界は周期的（FFT）に扱われる。
• 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
• signal_filter — py -3.11 examples/signal_filter.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
frequency)lowpass · sk_butterworth · 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).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.