frequency op• Data kinds: image → image
• Call: fullseye.apply(img, "highpass_image", 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)
A high-pass filter that blocks low frequencies (radius `<= 0.02+0.3*a) in the frequency domain and transforms the remainder back to real space via inverse FFT. Because the result is a zero-mean **signed** response, it is mapped to [0,1] with signed01 (0.5 represents zero, so it is normal for roughly half the pixels to fall below 0.5). Corresponds 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 が遮断半径(カットオフ周波数)を振る。b` は未使用。単純に
`> 0.5` で二値化するとほぼ半分の画素が黒に潰れるので注意(詳細は
`_sh_freq` の docstring)。
• 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 · 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.