vol_equalize — 3D gray op

• データ種: voxel → voxel

• 呼び出し: import fullseye as fs; fs.ledger.vol_equalize(vol, nbins=256, mask=None) (実装を直接呼ぶなら import volgray; volgray.vol_equalize(vol, nbins=256, mask=None)、台帳から引くなら ops3d.get("vol_equalize"))

使い方

Histogram equalisation of a volume (HALCON `equ_histo_image`).

Builds an *nbins*-bin histogram over the volume's `[min, max]` range,

takes its cumulative distribution as a monotone LUT, and maps every voxel

through it — the output lives in `(0, 1]` and its histogram is

(approximately) flat. With *mask* (thresholded at `> 0.5`, the volops

convention) the **histogram is computed from the masked voxels only while

the LUT is applied to the whole volume** — exactly the HALCON

`reduce_domain + equ_histo_image` domain behaviour, and the right

tool when a dominant background (e.g. air around a CT subject) would

otherwise swallow the whole dynamic range.

A constant volume is returned unchanged — normalising a flat volume

would amplify floating-point dust into full-scale garbage (fail-honest,

not fail-loud; see the module docstring).

Parameters

----------

vol : array_like, shape (D, H, W)

Input volume (coerced to float64; NaN/Inf rejected).

nbins : int

Histogram bins, `>= 2`. More bins = finer LUT (the mapping is

piecewise-constant per bin — an approximation, documented above).

mask : array_like, shape (D, H, W), optional

Histogram domain. Must match *vol*'s shape and select at least one

voxel (an empty domain has no histogram — fail-closed).

Returns

-------

ndarray, shape (D, H, W), float64

The equalised volume in `[0, 1]` (constant input: the input itself).

Raises

------

ValueError

Non-3-D / non-finite input, `nbins < 2`, a mask shape mismatch, or

an empty mask.

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。

実行できる例(この op を実際に呼ぶ検証済みサンプル)

• gray_window_level — py -3.11 examples_3d/gray_window_level.py

型が繋がる次の op(voxel を入力に取れる)

voxel_to_mips · voxel_to_mesh · signed_distance_field · to_points · sobel3d · hessian3d · curvature_maps · edt_jfa

同カテゴリ(gray)

vol_window_level · vol_gamma · vol_stretch

*Provenance: volgray.py — 3D 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)。*

© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.