region op• Data kinds: region → region
• Call: fullseye.apply(img, "r2_union1", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: union1 (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.*
*Knob a does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
*Knob b does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
Stages (the ops that come before → this op, left to right):
▸ r2_union1: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ r2_union1: other inputs (docs site)
Union of all connected components into a single mask (OR of labels).
Labels the foreground mask (> 0.5) into connected components with scipy.ndimage.label, turns label > 0 back into 1.0 and returns it as 1 mask. Since it is the union of all components, the result is the same as "the input normalised to 0/1" (the actual effect is binarising the values into 2 levels and removing non-finite values). a, b are unused.
The return value is a float64 0/1 mask of the same shape as the input. All zeros if there is no foreground. Grey values of 0.5 or less and NaN/Inf all become background. When a label image with several label values is received, the distinction between label numbers also disappears and it becomes a single foreground mask (to extract per label, use r3_label_to_region). In a pipeline its role is to make explicit that "the region is treated as 1 object"; component-wise selection (select_shape / r2_sort_region) is placed before this op.
• 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 r2_union1 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.