texture op• Data kinds: image → image
• Call: fullseye.apply(img, "structure_tensor_orientation", 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.*
*The output is shown in a viridis-like pseudo-colour (dark purple = low, yellow = high) so that a field of quantities — distance, phase, orientation, depth — can be read.*
Sweeping knob a (0.1 / 0.5 / 0.9, the other knob at its default):
▸ structure_tensor_orientation: knob a sweep (docs site)
Sweeping knob b (0.1 / 0.5 / 0.9, the other knob at its default):
▸ structure_tensor_orientation: knob b sweep (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ structure_tensor_orientation: 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 the local direction in which stripes run (principal axis of the structure tensor) mapped to [0,1].
0 and 1 both correspond to horizontal and 0.5 to vertical (orientation wraps around every 180 degrees, so 0 and 1 are the same orientation — note that differencing this output produces false steps at the seam).
a is the pre-derivative smoothing sigma (0.5-3.0 pixels), b the integration window rho (1.0-8.0 pixels). rho is "over how wide an area the orientation is considered aligned"; take it larger than the pitch of fibres or polishing marks.
Conditions of use: orientation can be defined only where the gradient is structurally biased. Pixels where the tensor's anisotropy is below 1e-6 relative to the trace (flat surfaces, isotropic noise) return 0.5 as "orientation undefined" — without a floor here, rounding dust on a uniform surface is amplified by arctan2 and changing the brightness by just 0.01 flips the orientation everywhere at once. Measure the reliability of the orientation separately with structure_tensor_coherence.
Uses: fibre orientation in fibre-reinforced materials, direction of rolling and polishing striations, wood grain, elongation direction of crystal grains. HALCON has no corresponding standalone op.
• gallery2d_texture_freq 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.
structure_tensor_orientation 0.50 0.50
▸ Load this pipeline · Load & run
• degenerate_inputs — py -3.11 examples/degenerate_inputs.py
• gallery2d_texture_freq — py -3.11 examples/gallery2d_texture_freq.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
texture)std_filter · local_bimodality · local_std · scale_select_std · bootstrap_std_error · structure_tensor_coherence · gabor · sk_frangi
*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.