frequency op• Data kinds: image → image
• Call: fullseye.apply(img, "lowpass", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
*The figure is the real output on a synthetic 128×128 input. Left: input, right: output (a non-image return value is shown as the value itself).*
Low-pass filter via FFT (blurring). No corresponding single HALCON op has been specified.
> The detailed description below is the original text — the summary and the headings are translated.
`a が遮断周波数 cutoff = 0.05 + 0.4a（正規化周波数、0〜0.5 がナイキストまでの範囲）を振る。b は未使用。2-D FFT で rad <= cutoff の低周波成分だけを残し、逆 FFT の実部を [0,1] に clip する。a が小さいほど強くぼける。境界は周期的（FFT の性質上、画像端は反対側と隣接するとみなされる）に扱われ、ndimage 系フィルタの reflect/edge` とは境界処理が異なる点に注意。
• 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.
The program below has been verified to run (same input as the figure). In Studio's help this block becomes buttons that load and run it on the spot.
lowpass 0.40 0.50
▸ Load this pipeline · Load & run
• 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)highpass · 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.