convert op• Data kinds: rgbimage → qimage
• Call: import quatimage; quatimage.rgb_to_quaternion(image_rgb) -> 'np.ndarray' (or opsquat.get("rgb_to_quaternion"))
Embed a colour image as pure quaternions `0 + R i + G j + B k`. → (H, W, 4).
Sangwine's 1996 encoding, and the entry point of the whole colour half of
this module: once a pixel is a quaternion, `q x conj(q)` rotates its colour
and :func:qft2 transforms the three channels as one hypercomplex signal
instead of three unrelated real ones.
The scalar (`w`) component is set to exactly zero — a *pure* quaternion —
because that is what makes the conjugation a 3-D rotation. Values are not
clamped: linear RGB after black-level subtraction legitimately goes negative,
and clipping it would change the colour direction, which is the quantity
every operator downstream reads.
Raises `ValueError: *image_rgb* is not a finite (H, W, 3)` numeric
array, is complex / bool / string-typed / masked, or exceeds
:data:MAX_PIXELS.
• 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
qimage as input)quaternion_to_rgb · quat_norm · quat_conjugate_image · quat_normalize_image · quat_image_multiply · monogenic_amplitude · monogenic_phase · monogenic_orientation
convert)*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.