polar_trans_region_inv — 2D `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)

polar_trans_region_inv: 入力 → 出力

*The figure is the real output on a synthetic 128×128 input. Left: input, right: output (a non-image return value is shown as the value itself).*

Usage

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）。

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.

Try it in Studio

The program below has been verified to run (same input as the figure). In Studio's help this block becomes buttons that load and run it on the spot.

threshold 0.50 0.50
polar_trans_region_inv 0.50 0.50

▸ Load this pipeline · Load & run

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 `region` as input)

identity · reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small

Same category (`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).*

polar_trans_region_inv — 2D geometry op