region op• Data kinds: region → region
• Call: fullseye.apply(img, "r3_clip_region", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: clip_region (the HALCON reference is a useful guide to its meaning and parameters)
*The figure is the actual output on a synthetic 128×128 input. Left: input, right: output. Point clouds are drawn as a top-down scatter (brightness = z), 1-D series as a line plot, volumes as the maximum-intensity projection along z, videos as the middle frame, complex images as magnitude; return values that are not pictures are shown as the values themselves.*
Sweeping knob a (0.1 / 0.5 / 0.9, the other knob at its default):
▸ r3_clip_region: knob a sweep (docs site)
Sweeping knob b (0.1 / 0.5 / 0.9, the other knob at its default):
▸ r3_clip_region: knob b sweep (docs site)
Stages (the ops that come before → this op, left to right):
▸ r3_clip_region: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ r3_clip_region: other inputs (docs site)
Clips the region with a rectangular window centred on the image (equivalent to HALCON clip_region).
a is the fraction of height to keep (0 to 1), b the fraction of width to keep (0 to 1). The window is placed at the image centre, and all region pixels outside the window are erased.
The window size is wh = max(1, round(a*H)) rows × ww = max(1, round(b*W)) columns, with its top-left at ((H-wh)//2, (W-ww)//2) (remainders lean to top/left). a, b are clipped to [0,1], 0.5 if non-finite. a=b=1 returns the input unchanged; even a=b=0 keeps the 1 central pixel (it never becomes all zero). The input is turned into a foreground mask with > 0.5, so grey values and NaN are treated as background.
Returns a float64 0/1 mask of the same shape as the input. Note that the window is based on the whole image, not on the region's bounding rectangle (if the region is in a corner of the image, a=b=0.5 may erase it entirely). For a relative clip based on the region, use hx_clip_region_rel. It erases outside the window; it does not make the window itself foreground (where there is no region it stays 0). Cutting the same central window on the image side is it_crop_domain (which uses 1 a for the same fraction vertically and horizontally); keeping contour points with a window is xg_crop_contours. On exception it falls back to a 0 mask, recorded in the backend_safe ledger (re-raised in strict mode).
• gallery2d_region 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 r3_clip_region 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_region — py -3.11 examples/gallery2d_region.py
region as input)identity · reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small
region)reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small · invert_region
*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.