access_channel — 2D color op

• Data kinds: color → image

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

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

Usage

Extracts a single channel from a multichannel image. Corresponds to HALCON's `access_channel` (accesses a single channel of a multichannel image).

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

a でチャンネル番号を 0(R)/1(G)/2(B) の 3 通りから選ぶ

（`min(2, int(a * 3))`）。b は未使用。

Detailed usage guide

• gallery2d_color_artistic family guide

Background guides (the physics and conventions behind this op)

• colorimetry — 測色と分光の知識 — 色は「分光 × 光源 × 観測者」でしか決まらない

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_color_artistic — py -3.11 examples/gallery2d_color_artistic.py

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

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

Same category (color)

cfa_to_rgb · trans_from_rgb · trans_to_rgb · linear_trans_color · principal_comp · rgb1_to_gray · rgb3_to_gray

*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.