fourier op• データ種: qimage → qimage
• 呼び出し: import quatimage; quatimage.iqft2(spectrum, side, mu=None) -> 'np.ndarray' (または opsquat.get("iqft2"))
Inverse quaternion Fourier transform of a centred spectrum. → (H, W, 4).
The exact inverse of :func:qft2 for the same side and the same mu:
measured round-trip error `2.22e-15` for both sides on a standard-normal
`(32, 32, 4) field. The kernel is exp(+mu * 2*pi*(...))` applied on the
side named, and the `1/(H*W)` normalisation is carried here, as in
`numpy.fft.ifft2`.
Using the wrong side does not raise. `iqft2(qft2(q, "left"), "right")`
returns a finite, plausible quaternion image that is simply not `q`:
measured `max|err| = 1.113` on a random colour image whose own range is
`0.9994 (another seed: 1.063 against 1.0), and — the dangerous case — only 0.054` against a range of
`1.076` on a grey-axis-dominated one, which is small enough to survive a
look at the picture. The `side` argument is required at both ends for
exactly this reason, and the two calls must agree: nothing in the data
records which transform produced it, so nothing downstream can catch the
mismatch for you.
Raises `ValueError: *spectrum* is not a valid (H, W, 4)` field;
*side* is not `'left' / 'right'`; *mu* is not a finite non-zero
3-vector.
• quaternion_monogenic ファミリ ガイド
• サンプルデータ カタログ(DL URL / ライセンス) — 2-D は skimage.data(BSD/public)+ 合成、3-D は実データ源(Stanford/PDS 等)の DL URL。
• 演算子の来歴・参考文献 — この op 族の元になった研究/手法の出典。
• アルゴリズムの正典(著者・年)と用途は上記ファミリ使い方ガイドに記載。
• quaternion_monogenic — py -3.11 examples/quaternion_monogenic.py
qimage を入力に取れる)quaternion_to_rgb · quat_norm · quat_conjugate_image · quat_normalize_image · quat_image_multiply · monogenic_amplitude · monogenic_phase · monogenic_orientation
fourier)*Provenance: quatimage.py — QUAT operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.