sk_swirl — 2D geometry op

• Data kinds: image → image

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

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

Usage

Swirl warp. A nonlinear geometric transform that rotates more strongly the closer a point is to the image center -- a distortion effect based on polar coordinate transformation.

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

HALCON の polar_trans_image(Transform an image to polar coordinates)に相当(近似。極座標画像そのものではなく、渦状に歪ませた直交座標画像を返す)。実装は `transform.swirl(v, strength=1+4*a, radius=30) を [0,1]` へ clip したもの —— a は渦の強さを 1〜5 に振る。渦の半径は 30 画素に固定。b は未使用。

Detailed usage guide

• gallery2d_geometry 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_geometry — py -3.11 examples/gallery2d_geometry.py

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

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

Same category (geometry)

rotate_img · rescale_img · affine_warp · mirror_image · transpose_region · rotate_image · zoom_image_factor · zoom_image_size

*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.