riesz op• Data kinds: qimage → image2d
• Call: import quatimage; quatimage.monogenic_amplitude(qimage) -> 'np.ndarray' (or opsquat.get("monogenic_amplitude"))
Local amplitude `sqrt(f^2 + R1^2 + R2^2)` of a monogenic signal. → (H, W).
The local contrast at the signal's scale, and the confidence map for
:func:monogenic_phase / :func:monogenic_orientation, which mean nothing
where this is at the rounding floor. Raw / unnormalised (a contrast is a
metric quantity), in the same spirit as `complexops.cx_magnitude`.
For a unit-contrast grating at the band centre it is exactly 1.0 (measured
spread 8.9e-16 over a 64x64 frame) and, unlike a squared oriented-filter
response, it is *isotropic*: rotating the grating does not change it.
Measured over eight grid-exact orientations the amplitude spans
`[0.99999999999999911, 1.0000000000000011]` — a total spread of 2.0e-15
across all of them, which is the isotropy claim as a number.
Raises `ValueError`: the input is not a valid quaternion field, or its
`k component is non-zero (see :func:_require_monogenic`).
• quaternion_monogenic 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.
• quaternion_monogenic — py -3.11 examples/quaternion_monogenic.py
image2d as input)riesz_transform · monogenic_signal
riesz)riesz_transform · monogenic_signal · monogenic_phase · monogenic_orientation
*Provenance: quatimage.py — QUAT 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.