region op• Data kinds: region → region
• Call: fullseye.apply(img, "fill_holes", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: fill_up (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):
▸ fill_holes: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ fill_holes: other inputs (docs site)
Fills holes within a region. Equivalent to HALCON's fill_up (Fill up holes in regions.).
a, b are unused. Turns every background pixel completely enclosed by foreground (a hole) into foreground (scipy.ndimage.binary_fill_holes). Background touching the image border is not regarded as a hole and is not filled.
Connectivity: the background used to decide holes is 4-connected (the default of scipy.ndimage.binary_fill_holes). Background connected only diagonally is not regarded as connected, so in a checkerboard every inner background pixel is filled as a hole (8x8: 32 -> 50 pixels; measured, it matches scipy's 4-connected reference down to the positions and does not match 8-connectivity). The 2nd implementation chose a different connectivity here, and this surfaced in a differential check.
• 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 fill_holes 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_region — py -3.11 examples/gallery2d_region.py
• poc_cell_counting — py -3.11 examples/poc_cell_counting.py
• poc_document_scan — py -3.11 examples/poc_document_scan.py
• poc_leaf_disease_area — py -3.11 examples/poc_leaf_disease_area.py
• poc_mesh_quality_repair — py -3.11 examples/poc_mesh_quality_repair.py
• poc_real_coin_metrology — py -3.11 examples/poc_real_coin_metrology.py
• poc_symmetry_restoration — py -3.11 examples/poc_symmetry_restoration.py
region as input)identity · reg_erode · reg_dilate · reg_open · reg_close · select_largest · remove_small · invert_region
region)reg_erode · reg_dilate · reg_open · reg_close · select_largest · remove_small · invert_region · dist_transform
*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.