wave op• Data kinds: image2d → measurement
• Call: import fullseye as fs; fs.ledger.wave_fringe_period(image, axis=1) (to call the implementation directly, import mathops; mathops.wave_fringe_period(image, axis=1); from the registry, opsmath.get("wave_fringe_period"))
The period of a striped image, measured back out of it (pixels).
Takes the mean profile along *axis*, removes the mean, and reads the dominant
frequency from the FFT with a parabolic interpolation on the log spectrum,
so the answer is not quantised to the FFT bin.
★Why this earns its place: it closes the loop on :func:wave_two_slit and
on any halftone or grating image — the period predicted by the closed form and
the period measured from the pixels are two different computations.
Returns a `measurement`: the period in pixels.
Raises `ValueError`: not a 2-D array; fewer than 8 samples along *axis*;
non-finite values; a profile with no variation (a flat image has no period).
Every mathops op validates its input before computing (nothing slips through silently):
• **complex input raises ValueError** — coercing to float64 silently discards the imaginary part (numpy only emits a ComplexWarning and returns a plausible-looking wrong real number). State .real/.imag/abs() explicitly, or use complexops, which handles complex data.
• **masked arrays with masked elements raise ValueError** — the implicit conversion that peels off the mask and uses the raw values underneath is refused. Say explicitly whether to fill or to drop.
• **NaN/Inf raises ValueError on every input** (refused with the count stated — it propagates through the whole result).
• Shapes are strict: 1-D and 2-D are never implicitly promoted or broadcast (a matrix in a vector slot, or a vector in a matrix slot, raises ValueError; reshape explicitly).
• Size cap: ops that take a matrix, and the stat_histogram bins, raise ValueError beyond mathops.MAX_ELEMENTS (2^26 ≈ 67 million elements).
• 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.
• poc_beats_fringes_and_screens — py -3.11 examples/poc_beats_fringes_and_screens.py
measurement as input)—
wave)wave_membrane_mode · wave_mode_frequencies · wave_nodal_lines · wave_two_slit · wave_grating_orders
*Provenance: mathops.py — MATH 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.