mirror of
https://github.com/visioncortex/vtracer.git
synced 2026-09-12 15:16:08 -07:00
Chris Tsang
c3f56a6339
Three refinements that make the watershed frontend a first-class citizen of both compositing modes and of interactive tuning: Stacked mode now stacks for real. Instead of one full-canvas background plus disjoint regions, the cut emits the merge tree itself: the root (whole canvas, mean color) first, then progressively finer ancestor regions, then the final regions on top — the same principle as the color clustering frontend, just with watershed-born clusters. Sub-pixel gaps between abutting regions therefore show their common ancestor's color rather than an unrelated backdrop, and overdraw stays seam-free. A painted-area budget (3x canvas) keeps pathological persistence chains from ballooning the stack; the root and final regions are always emitted so coverage never depends on it. Cutout is native. The watershed hierarchy already decided every merge, so the flattened partition reaches the mosaic untouched: merge_diff is 0 for watershed (the gradient-step re-merge still applies to the color path). Faces are exactly the cut regions. Re-cuts are cached. WatershedHierarchy is now public and split into build(img) — Kruskal, BPT, volume persistence; depends only on the image — and cut(detail, min_area), which is near-linear: region formation, graph-level small-basin absorption (region adjacencies, not pixel sweeps), then the merge tree. Session builds the hierarchy lazily on the first watershed render and re-cuts it on every watershed_detail or filter_speckle change: ~25 ms per re-cut vs ~40 ms rebuild on a 1400x775 photo, with the one-shot Frontend::segment path unchanged (build + cut), so Session output still equals the one-shot pipeline exactly. Tests: flatten-based stack invariants (solid bottom layer, full coverage, final regions topmost, exact region counts), hierarchy re-cut == one-shot, Session re-cut == one-shot across detail changes, and cutout keeping two regions one gradient step apart that the color path's merge would rejoin. Watershed goldens re-blessed for the new stack structure.