tb_quaternion_to_rgb — 2D `typed` op

• Data kinds: qimage → rgbimage

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

tb_quaternion_to_rgb: input → output

*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.*

*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).*

Stages (the ops that come before → this op, left to right):

▸ tb_quaternion_to_rgb: stages (docs site)

On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):

▸ tb_quaternion_to_rgb: other inputs (docs site)

Usage

Vector part of a quaternion image, as linear RGB. → (H, W, 3).

The inverse of :func:rgb_to_quaternion — and, by default, a *checked*

inverse. A quaternion image that picked up a scalar component somewhere (a

Hamilton product with a non-pure quaternion, a monogenic signal handed here

by mistake) is refused rather than silently truncated, because dropping

the `w` component is exactly the kind of loss that produces a plausible

picture from the wrong data. Pass `allow_scalar=True` to opt in to the

truncation when it is what you meant.

The tolerance is relative to the field's own peak modulus

(:data:_MONOGENIC_K_TOL, 1e-9): a quaternion image that really is pure

carries `|w|` at the 1e-17 level after a round trip through two FFTs, and

anything with a meaningful scalar part is many orders above that. Nothing

real lives in between.

Raises `ValueError: *qimage* is not a finite (H, W, 4)` array; or

it has a non-negligible scalar part and `allow_scalar` is False.

Typed bridge of the quat op `quaternion_to_rgb 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.

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.

img_to_rgb 0.50 0.50
tb_rgb_to_quaternion 0.50 0.50
tb_quaternion_to_rgb 0.50 0.50

▸ Load this pipeline · Load & run

Runnable examples (verified samples that actually call this op)

The examples below call the underlying ledger op quaternion_to_rgb. This bridge op is the same implementation adapted to the fn(v, a, b) convention, so the behaviour carries over unchanged (only the call form differs).

• quaternion_monogenic — py -3.11 examples/quaternion_monogenic.py

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

identity · tb_wetness · tb_sensor_capture · tb_specular_diffuse_split · tb_specular_coefficient_map · tb_specular_free_transform · tb_rgb_to_quaternion

Same category (`typed`)

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

*Provenance: ops.py — 2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

tb_quaternion_to_rgb — 2D typed op