feat(slices): implement def polys_iou

scanslicer/slices.py

@@ -181,3 +181,42 @@ class PhotoSlice:
         )
         self.normalize_top_left()
         self.side_handles_enabled = True
+
+
+# polys_iou: function definition for ScanSlicer behavior.
+def polys_iou(poly1, poly2):
+    a = np.array(poly1, dtype=np.float32).reshape(-1, 2)
+    b = np.array(poly2, dtype=np.float32).reshape(-1, 2)
+
+    if len(a) < 3 or len(b) < 3:
+        return 0.0
+
+    # Fast reject for disjoint axis-aligned bounds.
+    a_min_x = float(np.min(a[:, 0]))
+    a_max_x = float(np.max(a[:, 0]))
+    a_min_y = float(np.min(a[:, 1]))
+    a_max_y = float(np.max(a[:, 1]))
+    b_min_x = float(np.min(b[:, 0]))
+    b_max_x = float(np.max(b[:, 0]))
+    b_min_y = float(np.min(b[:, 1]))
+    b_max_y = float(np.max(b[:, 1]))
+    if a_max_x < b_min_x or b_max_x < a_min_x or a_max_y < b_min_y or b_max_y < a_min_y:
+        return 0.0
+
+    area_a = cv2.contourArea(a)
+    area_b = cv2.contourArea(b)
+    if area_a <= 0 or area_b <= 0:
+        return 0.0
+
+    try:
+        inter_area, _ = cv2.intersectConvexConvex(a, b)
+    except cv2.error:
+        return 0.0
+
+    if inter_area <= 0:
+        return 0.0
+
+    union_area = area_a + area_b - inter_area
+    if union_area <= 0:
+        return 0.0
+    return float(inter_area / union_area)