tb_monogenic_amplitude — 2D typed op

Data kinds: qimageimage

Call: fullseye.apply(img, "tb_monogenic_amplitude", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])

Usage

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`).

Typed bridge of the quat op `monogenic_amplitude into the 2-D evolution registry: the same implementation, called under the op(v, a, b) convention. This op has no tunable parameter; a and b` are unused.

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.

Runnable examples (verified samples that actually call this op)

• (none yet)

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

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

Same category (typed)

tb_points_to_voxel · tb_estimate_point_normals · tb_iss_keypoints · tb_angle_3points · tb_project_points · tb_render_point_depth · tb_statistical_outlier_removal · tb_radius_outlier_removal


*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.