Initial public release

backend/tests/test_detection_tile_seam_handling.py

@@ -0,0 +1,125 @@
+"""Detections that straddle a tile seam must not become two half buildings.
+
+Tiling uses a fixed overlap. An object wider than that overlap is truncated by
+both tiles, so the two boxes barely intersect and plain IoU suppression keeps
+them both: two false positives plus one missed footprint for every seam
+building. The suppressor therefore also compares overlap against the smaller
+box, and truncated boxes that sit against an interior tile edge are dropped in
+favour of the neighbouring tile's complete view.
+"""
+
+from __future__ import annotations
+
+from shapely.geometry import box
+
+from app.services.detection_service import DetectionService
+
+
+def _candidate(name: str, geometry, confidence: float, *, tile_index: int = 0, tile_bounds=None):
+    return {
+        "class_name": "building",
+        "confidence": confidence,
+        "geometry": geometry,
+        "bbox": [0.0, 0.0, 1.0, 1.0],
+        "source_tile_path": f"/tiles/tile_{tile_index:04d}.tif",
+        "properties": {"tile_index": tile_index, "name": name},
+        "tile_bounds": tile_bounds,
+    }
+
+
+def test_identical_overlapping_predictions_are_still_suppressed() -> None:
+    kept = DetectionService._suppress_duplicate_candidates(
+        [
+            _candidate("a", box(0.0, 0.0, 1.0, 1.0), 0.7),
+            _candidate("b", box(0.02, 0.02, 1.02, 1.02), 0.9),
+        ],
+        iou_threshold=0.5,
+    )
+
+    assert [item["properties"]["name"] for item in kept] == ["b"]
+
+
+def test_a_box_contained_in_a_larger_one_is_suppressed() -> None:
+    """A truncated seam half sits inside the complete box from the next tile."""
+
+    complete = box(0.0, 0.0, 10.0, 10.0)
+    truncated_half = box(0.0, 0.0, 4.0, 10.0)  # IoU with ``complete`` is 0.4
+
+    kept = DetectionService._suppress_duplicate_candidates(
+        [
+            _candidate("complete", complete, 0.88),
+            _candidate("truncated", truncated_half, 0.61),
+        ],
+        iou_threshold=0.5,
+    )
+
+    assert [item["properties"]["name"] for item in kept] == ["complete"]
+
+
+def test_genuinely_adjacent_buildings_are_both_kept() -> None:
+    """Terraced houses touch but do not contain one another."""
+
+    kept = DetectionService._suppress_duplicate_candidates(
+        [
+            _candidate("left", box(0.0, 0.0, 10.0, 10.0), 0.9),
+            _candidate("right", box(10.0, 0.0, 20.0, 10.0), 0.85),
+        ],
+        iou_threshold=0.5,
+    )
+
+    assert sorted(item["properties"]["name"] for item in kept) == ["left", "right"]
+
+
+def test_different_classes_are_never_merged() -> None:
+    first = _candidate("a", box(0.0, 0.0, 10.0, 10.0), 0.9)
+    second = _candidate("b", box(0.0, 0.0, 10.0, 10.0), 0.8)
+    second["class_name"] = "solar_panel"
+
+    kept = DetectionService._suppress_duplicate_candidates([first, second], iou_threshold=0.5)
+
+    assert len(kept) == 2
+
+
+def test_boxes_clipped_by_an_interior_tile_edge_are_dropped() -> None:
+    """The overlapping neighbour tile still sees the whole object."""
+
+    tile = box(0.0, 0.0, 10.0, 10.0)
+    raster = box(0.0, 0.0, 30.0, 10.0)
+
+    candidates = [
+        # Sits against the tile's right edge: truncated by the tile, not real.
+        _candidate("edge", box(9.0, 2.0, 10.0, 4.0), 0.8, tile_bounds=tile.bounds),
+        # Comfortably inside the tile.
+        _candidate("interior", box(2.0, 2.0, 4.0, 4.0), 0.8, tile_bounds=tile.bounds),
+    ]
+
+    kept = DetectionService._drop_tile_edge_truncations(
+        candidates, raster_bounds=raster.bounds, tolerance=0.001
+    )
+
+    assert [item["properties"]["name"] for item in kept] == ["interior"]
+
+
+def test_boxes_against_the_raster_edge_are_kept() -> None:
+    """No neighbouring tile exists there, so the box is all the evidence there is."""
+
+    tile = box(0.0, 0.0, 10.0, 10.0)
+    raster = box(0.0, 0.0, 10.0, 10.0)
+
+    candidates = [_candidate("edge", box(9.0, 2.0, 10.0, 4.0), 0.8, tile_bounds=tile.bounds)]
+
+    kept = DetectionService._drop_tile_edge_truncations(
+        candidates, raster_bounds=raster.bounds, tolerance=0.001
+    )
+
+    assert [item["properties"]["name"] for item in kept] == ["edge"]
+
+
+def test_edge_filter_keeps_candidates_without_tile_bounds() -> None:
+    candidates = [_candidate("unknown", box(2.0, 2.0, 4.0, 4.0), 0.8, tile_bounds=None)]
+
+    kept = DetectionService._drop_tile_edge_truncations(
+        candidates, raster_bounds=(0.0, 0.0, 30.0, 10.0), tolerance=0.001
+    )
+
+    assert len(kept) == 1