morphology op• Data kinds: image → image
• Call: fullseye.apply(img, "local_thickness", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
*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):
▸ local_thickness: knob a sweep (docs site)
Sweeping knob b (0.1 / 0.5 / 0.9, the other knob at its default):
▸ local_thickness: knob b sweep (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ local_thickness: other inputs (docs site)
*The 4th column is a colour (H,W,3) input. This op handles colour without crossing channels (it does not convolve the colour channel as a third spatial axis).*
Returns each foreground pixel filled with "the diameter of the largest circle that can cover it" (local thickness).
b is the threshold above which the bright side counts as foreground (0.1–0.9). a is the upper radius limit measured (1–12 pixels), and the output is divided by that limit to fit in [0,1] —— when you need absolute values, recover the limit from a and multiply back.
A classic quantity that gives particle size, pore size and wall thickness as "a single map"; it is the same as morphological
granulometry: if a pixel has the value r, that pixel survives an opening with a disc of radius r. The implementation is straightforward: the distance transform gives the inscribed-circle radius, and in descending order of radius each circle is written into the area it covers.
Applicability: (1) The foreground is decided by a single threshold, so with uneven illumination the thickness becomes biased by location —— flatten first with local_threshold or similar. (2) Structures thicker than the limit a level off at the limit (whether it saturates shows in the output maximum sticking at 1.0).
(3) It is a pixel-unit quantity, so once the diameter drops below 3 pixels the quantization step exceeds 30%.
Uses: pore-size distribution in casting voids and foams, powder particle size, detection of thin-walled sections, fibre thickness. The 3-D version is vol_wall_thickness in ops3d. HALCON has no corresponding single op.
• gallery2d_morphology 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.
local_thickness 0.35 0.50
▸ Load this pipeline · Load & run
• gallery2d_morphology — py -3.11 examples/gallery2d_morphology.py
• poc_bone_trabecular_thickness — py -3.11 examples/poc_bone_trabecular_thickness.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
morphology)gerode · gdilate · gopen · gclose · runlength_smear · tophat · bothat · morph_grad
*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.