geometry op• Data kinds: region → region
• Call: fullseye.apply(img, "polar_trans_region_inv", 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_region_inv (the HALCON reference is a useful guide to its meaning and parameters)
Inverse-transforms a polar representation back to ordinary rectangular (Cartesian) coordinates (the inverse-mapping mode of `cv2.warpPolar). Fills the area outside the disk of radius min(h,w)/2 from the center with 0, then converts back to a binary region via _rebinarise with a 0.5 threshold. a and b are unused (shares the polar_inv branch of _sh_geom with polar_trans_image_inv`).
> The detailed description below is the original text — the summary and the headings are translated.
HALCON の `polar_trans_region_inv（極座標領域を元のデカルト座標系の領域に戻す演算）に相当。実装上、円盤境界付近 1 画素程度は補間の丸めで非決定的になりうるため外側を明示的に 0 で塗って安全側に倒している（2026-09-02 修正済み、詳細は _sh_geom の polar_inv` 分岐のコメント参照）。
• gallery2d_geometry family guide
• 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.
• gallery2d_geometry — py -3.11 examples/gallery2d_geometry.py
region as input)identity · reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small
geometry)rotate_img · rescale_img · affine_warp · sk_swirl · mirror_image · transpose_region · rotate_image · zoom_image_factor
*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.