geometry op• Data kinds: region → region
• Call: fullseye.apply(img, "mirror_region", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: mirror_region (the HALCON reference is a useful guide to its meaning and parameters)

*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).*
Flips (mirrors) the region. The axis is chosen by a: a<0.34 flips vertically (`flipud), 0.34<=a<0.67 flips horizontally (fliplr), otherwise it transposes (diagonal flip, x.T). b is unused. Since flipping doesn't change values, _rebinarise` is effectively a no-op.
> The detailed description below is the original text — the summary and the headings are translated.
HALCON の `mirror_region`(軸を指定して領域を反射する演算)に相当。HALCON は軸位置を任意に指定できるが、この実装は画像中心を通る 3 種類の軸(縦/横/対角)に固定されている近似。
• 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.
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 mirror_region 0.50 0.50
▸ Load this pipeline · Load & run
• 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.