frequency op• Data kinds: image → image
• Call: fullseye.apply(img, "fft_image", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: fft_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.*
*The output is shown in a viridis-like pseudo-colour (dark purple = low, yellow = high) so that a field of quantities — distance, phase, orientation, depth — can be read.*
*Knob a does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
*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):
▸ fft_image: other inputs (docs site)
*No colour (H,W,3) input is shown: this op treats the colour channel as a third spatial axis (it crosses channels). Call it per channel.*
An image obtained by compressing the power spectrum of the 2D FFT with `log1p(|F|) and normalizing it. Already fftshift-ed so the low-frequency (DC) component sits at the center. Used to visualize the spatial frequency of periodic noise or texture. Corresponds to HALCON's fft_image` (Compute the fast Fourier transform of an image).
> The detailed description below is the original text — the summary and the headings are translated.
`a, b` は未使用 ―― 画像全体に対するグローバルな FFT で、窓関数や
帯域選択のような調整点は無い。
Blank frame (measured): feeding an image of uniform brightness gives an empty result — every pixel is background (0) — regardless of the brightness. Pure white and pure black behave alike; brightness by itself detects nothing.
• 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.
fft_image 0.40 0.50
▸ Load this pipeline · Load & run
• degenerate_inputs — py -3.11 examples/degenerate_inputs.py
• gallery2d_texture_freq — py -3.11 examples/gallery2d_texture_freq.py
• poc_moire_screen — py -3.11 examples/poc_moire_screen.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
frequency)lowpass · highpass · sk_butterworth · 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.