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)
*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).*
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.
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.
highpass_image 0.40 0.50
▸ Load this pipeline · Load & run
• 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.