fourier_smooth — SHAPE2D descriptor op

• Data kinds: pairs → pairs

• Call: import fullseye as fs; fs.ledger.fourier_smooth(points, keep) (to call the implementation directly, import fourierdesc; fourierdesc.fourier_smooth(points, keep); from the registry, opsshape2d.get("fourier_smooth"))

Usage

Smooths a contour by band-limiting it with a complex FFT.

Treats the contour as the complex signal z(t)=x(t)+i·y(t), applies an FFT, keeps only the keep low frequencies (and their symmetric components), and transforms back. The smaller keep is, the smoother (high frequencies = detail/noise are dropped). If keep is at least the total number of frequencies, it is the identity. Returns (N,2) with the same number of points as the input.

Detailed usage guide

• shape_description_2d family guide

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.

• The canonical algorithm (author, year) and its uses are named in the family usage guide above.

Runnable examples (verified samples that actually call this op)

• contour_fourier — py -3.11 examples/contour_fourier.py

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

elliptic_fourier · contour_fourier_complex · add_frame_corners · warp_tps_image · warp_piecewise_affine · morph · morph_sequence

Same category (descriptor)

elliptic_fourier · reconstruct · invariants · normalize · descriptor_distance · from_xld · contour_fourier_complex · contour_epicycle_chain

*Provenance: fourierdesc.py — SHAPE2D 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.