descriptor op• Data kinds: matrix → pairs
• Call: import fullseye as fs; fs.ledger.contour_epicycle_chain(spectrum, phase, order='frequency') (to call the implementation directly, import fourierdesc; fourierdesc.contour_epicycle_chain(spectrum, phase, order='frequency'); from the registry, opsshape2d.get("contour_epicycle_chain"))
Returns the chain of rotating pendulums at phase t (pairs).
Arguments:
spectrum: (2K+1, 3) from contour_fourier_complex.
phase: t (1 turn = 1.0).
order: "frequency" = stack from low frequency (the textbook picture) /
"amplitude" = in order of decreasing amplitude (resemble with few terms).
Returns: pairs of (M+1, 2) ((row, col) order). Row 0 is the centre of the first arm, row m is the tip of the m-th arm (= the centre of the next arm), and the last row is the pen tip; it is exactly a point of the reconstructed contour. The length of arm m is |c_k|, its angle 2π k t + arg c_k.
• shape_description_2d 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.
• poc_one_stroke_epicycles — py -3.11 examples/poc_one_stroke_epicycles.py
pairs as input)elliptic_fourier · fourier_smooth · contour_fourier_complex · add_frame_corners · warp_tps_image · warp_piecewise_affine · morph · morph_sequence
descriptor)elliptic_fourier · reconstruct · invariants · normalize · descriptor_distance · fourier_smooth · from_xld · contour_fourier_complex
*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.