feat: add deterministic marker-based size bucketing

bookmark/sizing.py

@@ -0,0 +1,39 @@
+from dataclasses import dataclass
+
+import numpy as np
+
+
+@dataclass(frozen=True)
+class MarkerRegion:
+    name: str
+    bucket: str
+    x: int
+    y: int
+    width: int
+    height: int
+
+
+def _mean_region_diff(frame: np.ndarray, reference_frame: np.ndarray, marker: MarkerRegion) -> float:
+    frame_region = frame[marker.y:marker.y + marker.height, marker.x:marker.x + marker.width]
+    reference_region = reference_frame[marker.y:marker.y + marker.height, marker.x:marker.x + marker.width]
+    diff = np.abs(frame_region.astype(int) - reference_region.astype(int))
+    return float(diff.mean())
+
+
+def determine_size_bucket(
+    frame: np.ndarray,
+    reference_frame: np.ndarray,
+    markers: list[MarkerRegion],
+    threshold: float = 30.0,
+) -> str:
+    """
+    `markers` must be ordered smallest -> largest bucket boundary. Returns
+    the bucket of the largest boundary whose marker region is occluded
+    (covered by the book) relative to `reference_frame`. Defaults to the
+    smallest bucket if no marker is occluded.
+    """
+    bucket = markers[0].bucket
+    for marker in markers:
+        if _mean_region_diff(frame, reference_frame, marker) > threshold:
+            bucket = marker.bucket
+    return bucket

tests/test_sizing.py

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+import numpy as np
+
+from bookmark.sizing import MarkerRegion, determine_size_bucket
+
+
+def make_reference(size=100, color=200):
+    return np.full((size, size, 3), color, dtype=np.uint8)
+
+
+MARKERS = [
+    MarkerRegion(name="small_boundary", bucket="small", x=0, y=0, width=10, height=10),
+    MarkerRegion(name="medium_boundary", bucket="medium", x=50, y=0, width=10, height=10),
+    MarkerRegion(name="large_boundary", bucket="large", x=0, y=50, width=10, height=10),
+]
+
+
+def occlude(frame, marker, color=50):
+    frame = frame.copy()
+    frame[marker.y:marker.y + marker.height, marker.x:marker.x + marker.width] = color
+    return frame
+
+
+def test_no_markers_occluded_returns_smallest_bucket():
+    reference = make_reference()
+    frame = reference.copy()
+    assert determine_size_bucket(frame, reference, MARKERS) == "small"
+
+
+def test_only_small_marker_occluded_returns_small():
+    reference = make_reference()
+    frame = occlude(reference, MARKERS[0])
+    assert determine_size_bucket(frame, reference, MARKERS) == "small"
+
+
+def test_small_and_medium_occluded_returns_medium():
+    reference = make_reference()
+    frame = occlude(reference, MARKERS[0])
+    frame = occlude(frame, MARKERS[1])
+    assert determine_size_bucket(frame, reference, MARKERS) == "medium"
+
+
+def test_all_markers_occluded_returns_large():
+    reference = make_reference()
+    frame = reference.copy()
+    for marker in MARKERS:
+        frame = occlude(frame, marker)
+    assert determine_size_bucket(frame, reference, MARKERS) == "large"