cv_gradient — 2D morphology op

• Data kinds: image → image

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

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

Usage

Morphological gradient (OpenCV implementation). "Dilation result minus erosion result" extracts only the outline (border) of regions - a contour extraction method distinct from ordinary derivative-based edge detection.

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

HALCON の gray_range_rect(Determine the gray value range within a rectangle.)に相当(近似。矩形窓内の最大-最小レンジを取る点は同じ発想)。実装は `cv2.morphologyEx(v, MORPH_GRADIENT, se) を正規化したもの、se は楕円形でサイズ 3+2*int(a*3)` —— a は構造要素サイズを 3〜9 に振る。b は未使用。

Detailed usage guide

• gallery2d_morphology 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_morphology — py -3.11 examples/gallery2d_morphology.py

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

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

Same category (morphology)

gerode · gdilate · gopen · gclose · tophat · bothat · morph_grad · sk_area_opening

*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.