threshold op• Data kinds: image2d → table
• Call: import fullseye as fs; fs.ledger.threshold_isodata(image, *, nbins: 'int' = 256, max_iter: 'int' = 1000) -> 'Dict[str, object]' (to call the implementation directly, import seggraph; seggraph.threshold_isodata(image, *, nbins: 'int' = 256, max_iter: 'int' = 1000) -> 'Dict[str, object]'; from the registry, opssegmentation.get("threshold_isodata"))
ISODATA (Ridler–Calvard 1978): iterates t ← (μ_≤t + μ_>t)/2 on the pixel values until the partition stops changing (initial value = mean) (threshold_isodata).
Once the partition stops changing, t does not move even when μ is recomputed = the fixed point t = (μ_low + μ_high)/2 holds exactly (residual = 0). Fixed points on the histogram (same as skimage: "at bin centre c, 0 ≤ (μ_≤c + μ_>c)/2 − c < bin width") are also returned in fixed_points.
Returns: threshold, mask = image > t, mu_low / mu_high, residual, n_iter, fixed_points.
• halcon_segmentation family guide
• graph_hierarchy_and_thresholds — Segmentation from graph, hierarchy and threshold theorems — what is exact, and where the partition breaks down
• 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.
• poc_graph_hierarchy_segmentation — py -3.11 examples/poc_graph_hierarchy_segmentation.py
table as input)threshold)threshold_triangle · threshold_kittler · threshold_kapur
*Provenance: seggraph.py — SEGMENTATION 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.