polar_trans_image_inv — 2D `geometry` op

• Data kinds: image → image

• Call: fullseye.apply(img, "polar_trans_image_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_image_inv (the HALCON reference is a useful guide to its meaning and parameters)

polar_trans_image_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 transformation from polar to Cartesian coordinates (`cv2.warpPolar + WARP_INVERSE_MAP). The inverse mapping of polar_trans_image; the area outside the disk of radius min(H,W)/2 is filled with 0. A bug where "pixels not written by cv2 were returned uninitialized" was fixed on 2026-09-02 (it had been reading the passed-in dst instead of the return value, so values changed on every run — see the in-code comments for details). Corresponds to HALCON's polar_trans_image_inv` (Transform an image in polar coordinates back to Cartesian coordinates).

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

`a, b` は未使用 ―― 中心・半径は画像サイズから自動的に決まる。

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.

polar_trans_image_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 `image` as input)

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

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_image_inv — 2D geometry op