MaskAnnotator paints CompactMask detections into their bounding-box crop, but
HaloAnnotator never got that path: it materialized every mask full-frame, painted
via full-frame boolean indexing, and built its foreground mask as a 2M-element
Python list per frame. Extract the shared compact/dense painting into a single
_paint_masks_by_area helper used by both annotators. On a 1080p frame with 30
masks, HaloAnnotator on CompactMask runs about 4x faster; output is unchanged.
- Replace in-place `union` param with `collect_union: bool` return value;
HaloAnnotator now captures the returned union array
- Add Google-style Args/Returns to `_paint_masks_by_area` docstring
- Fix HaloAnnotator.annotate() example (was maskless → no-op) and scene arg wording
- Add section comment above shared helper for discoverability
- Add union accumulation tests (dense + CompactMask paths via collect_union=True)
- Add test documenting out-of-bbox True-pixel divergence between compact and dense
- Add image-edge bbox test for CompactMask annotators
- Move helper tests into TestPaintMasksByArea and TestCompactMaskParity classes
- Rename test_annotate_with_empty_masks → test_annotate_with_all_false_mask
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Co-authored-by: jirka <6035284+Borda@users.noreply.github.com>
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
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