lf_epi_slope — LIGHTFIELD `depth` op

• データ種: lightfield → image2d

• 呼び出し: import lightfield; lightfield.lf_epi_slope(lf, *, window=9, min_energy=1e-10) (または opslightfield.get("lf_epi_slope"))

使い方

EPI の線の向きから画素ごとの傾きを出す(構造テンソル、1 パス)。

> 以下の詳細説明は原文のままです —— 要約と見出しは訳出済み。

A scene point traces a straight line in the epipolar-plane image

(:func: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

:func: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*.

詳しい使い方ガイド

• lightfield_depth ファミリガイド

参考(サンプルデータ・文献)

• サンプルデータカタログ(DL URL / ライセンス) — 2-D は skimage.data(BSD/public)+ 合成、3-D は実データ源(Stanford/PDS 等)の DL URL。

• 演算子の来歴・参考文献 — この op 族の元になった研究/手法の出典。

• アルゴリズムの正典(著者・年)と用途は上記ファミリ使い方ガイドに記載。

実行できる例(この op を実際に呼ぶ検証済みサンプル)

• lightfield_depth — py -3.11 examples/lightfield_depth.py

型が繋がる次の op(`image2d` を入力に取れる)

lf_from_mla · lf_disparity_to_depth · lf_all_in_focus

同カテゴリ(`depth`)

lf_depth_from_focus · lf_disparity_to_depth · lf_all_in_focus · lf_plenoptic_design

*Provenance: lightfield.py — LIGHTFIELD operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。*

lf_epi_slope — LIGHTFIELD depth op

使い方