equalize — 2D gray op

• Data kinds: image → image

• Call: fullseye.apply(img, "equalize", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])

• HALCON equivalent: equ_histo_image (the HALCON reference is a useful guide to its meaning and parameters)

Usage

Histogram equalization (linearization). Equivalent to HALCON's `equ_histo_image` (Histogram linearization of images).

> The detailed description below is the original text — the summary and the headings are translated.

`a, b は未使用。[0,1] を 256 ビンに分けたヒストグラムの累積分布関数（CDF）を求め、各画素値をその CDF で置き換えることで、出力のヒストグラムがほぼ一様になるよう引き伸ばす。コントラストが低い（値域が狭い）画像を見やすくするのに使う。全画素が同一値だと CDF が定義できず cdf[-1]` が 0 になり、変換は事実上恒等（変化なし）になる。

Detailed usage guide

• gallery2d_gray_arith 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)

• gallery2d_gray_arith — py -3.11 examples/gallery2d_gray_arith.py

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

identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter

Same category (gray)

gamma · invert · scale_clip · sigmoid · clahe · sk_adapthist · sk_enhance_contrast · sk_autolevel

*Provenance: ops.py — 2D 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.