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 actual output on a synthetic 128×128 input. Left: input, right: output. Point clouds are drawn as a top-down scatter (brightness = z), 1-D series as a line plot, volumes as the maximum-intensity projection along z, videos as the middle frame, complex images as magnitude; return values that are not pictures are shown as the values themselves.*
Sweeping knob a (0.1 / 0.5 / 0.9, the other knob at its default):
▸ highpass_image: knob a sweep (docs site)
*Knob b does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ highpass_image: other inputs (docs site)
*The 4th column is a colour (H,W,3) input. This op handles colour without crossing channels (it does not convolve the colour channel as a third spatial axis).*
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)。
Border handling: wrap around to the opposite side (periodic) (measured; tools/impl2/border_probe.py).
• 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
• poc_river_surface_velocity — py -3.11 examples/poc_river_surface_velocity.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.