features op• Data kinds: region → feature
• Call: fullseye.apply(img, "rectangularity", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: rectangularity (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):
▸ rectangularity: stages (docs site)
Rectangularity. A rectangle with the same first and second order moments is constructed and the area of the difference to the region is normalised by the area of that rectangle (1 - |region XOR rectangle| / |rectangle|); it is 1 for a rectangle. The same definition as HALCON's rectangularity (Shape factor for the rectangularity of a region.).
★Until 2026-09-26 it was the ratio to the axis-parallel bounding rectangle (extent in skimage). Since it ignores orientation, merely rotating the same rectangle by 30 degrees dropped 1.000 to 0.359 (HALCON stays at 0.998). docs/hardening/halcon-named-shape-factors.md.
★For shapes such as a square or a circle, whose orientation is not fixed by the 2nd-order moments, there are as many "rectangles with the same moments" as there are orientations, and the definition does not fix the orientation. Here the orientation with the largest overlap is chosen -- fitting at an arbitrary orientation would give a square 0.651, contradicting HALCON's "1 for a rectangle". HALCON also states that for such shapes it underestimates by up to 10%.
a, b are unused.
• gallery2d_features 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 rectangularity 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_features — py -3.11 examples/gallery2d_features.py
• shape_factors_closed_form — py -3.11 examples/shape_factors_closed_form.py
feature as input)features)effective_bit_depth · blob_count · area_frac · count_contours · total_length · vol_count · sk_euler · sk_entropy_feat
*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.