depth op• Data kinds: lightfield → image2d
• Call: import fullseye as fs; fs.ledger.lf_epi_slope(lf, *, window=9, min_energy=1e-10) (to call the implementation directly, import lightfield; lightfield.lf_epi_slope(lf, *, window=9, min_energy=1e-10); from the registry, opslightfield.get("lf_epi_slope"))
• Return value through the ledger: fullseye.ledger.lf_epi_slope(...) returns only the declared out type image2d (the underlying function also returns auxiliary values). When you need what was dropped, use fullseye.ledger.lf_epi_slope.raw(...) or call lightfield.lf_epi_slope directly.
Per-pixel slope from the EPI line orientation (structure tensor, one pass).
A scene point traces a straight line in the epipolar-plane image (lf_epi), so along that line the intensity is constant:
E_u + s * E_x = 0. Accumulating that constraint over the whole angular grid and a window x window spatial neighbourhood gives the closed-form least-squares slope s = -(J_ux + J_vy) / (J_xx + J_yy) with J_ab = sum(E_a * E_b) — one pass over the light field, no sweep, both the horizontal and vertical EPI directions pooled.
This estimator is biased, and the bias is the reason to also run lf_depth_from_focus. It is ordinary (not total) least squares on finite differences, so it needs the EPI line to advance less than roughly one texture correlation length per view. Measured 2026-09-01 on 5x5x64x64 synthetic fields, median over the interior: with texture sigma = 1.5 px, true +1.00 -> +1.0004, +0.50 -> +0.5285, +1.50 -> +1.3018, +2.00 -> +1.4614; with sigma = 5.0 px the same slopes give +1.0003, +0.5029, +1.4827, +1.9482. Integer slopes on a wrapped field come back within 4e-4 and s = 0 is exact; |s| > 1 is under-estimated, by 27% at s = 2 on the roughest texture. Use it as a fast dense initialiser, not as the final word.
Returns (slope_map, energy): the (H, W) slope map and the (H, W) gradient energy J_xx + J_yy that was the denominator. Pixels whose energy is below *min_energy* have no measurable parallax (a flat patch of sky); their slope is set to 0 and their energy reported as-is, so you threshold on energy instead of being handed a plausible-looking number divided by ~0.
Raises ValueError: *lf* not a valid light field, an angular/spatial shape where *neither* EPI direction carries information (the horizontal EPI needs U >= 2 and W >= 2, the vertical needs V >= 2 and H >= 2), an even or non-positive *window*, a non-positive *min_energy*.
• lightfield_depth 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.
• lightfield_depth — py -3.11 examples/lightfield_depth.py
• poc_lightfield_depth — py -3.11 examples/poc_lightfield_depth.py
image2d as input)lf_from_mla · lf_disparity_to_depth · lf_all_in_focus
depth)lf_depth_from_focus · lf_disparity_to_depth · lf_all_in_focus · lf_plenoptic_design
*Provenance: lightfield.py — LIGHTFIELD 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.