fft_image — 2D `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)

fft_image: 入力 → 出力

*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).*

Usage

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。

Detailed usage guide

• gallery2d_texture_freq family guide

References (sample data, literature)

• 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.

Try it in Studio

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

Runnable examples (verified samples that actually call this op)

• gallery2d_texture_freq — py -3.11 examples/gallery2d_texture_freq.py

• poc_moire_screen — py -3.11 examples/poc_moire_screen.py

Ops the type connects to (they accept `image` as input)

identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter

Same category (`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).*

fft_image — 2D frequency op