Simplify box_non_max_merge

Author: Linas Kondrackis

supervision/detection/utils.py

@@ -292,7 +292,7 @@ def box_non_max_merge(
         Dict[int, List[int]]: Mapping from prediction indices
         to keep to a list of prediction indices to be merged.
     """
-    keep_to_merge_list = {}
+    keep_to_merge_list: Dict[int, List[int]] = {}
 
     scores = predictions[:, 4]
     order = scores.argsort()
@@ -307,17 +307,11 @@ def box_non_max_merge(
             break
 
         ious = box_iou_batch(predictions[order][:, :4], merge_candidate[:, :4])
+        ious = ious.flatten()
 
-        below_threshold = (ious < iou_threshold).astype(np.uint8)
-        matched_box_indices = np.flip(order[np.where(below_threshold == 0)[0]])
-        unmatched_indices = order[np.where(below_threshold == 1)[0]]
-
-        order = unmatched_indices[scores[unmatched_indices].argsort()]
-
-        keep_to_merge_list[idx.tolist()] = []
-
-        for matched_box_ind in matched_box_indices.tolist():
-            keep_to_merge_list[idx.tolist()].append(matched_box_ind)
+        above_threshold = ious >= iou_threshold
+        keep_to_merge_list[idx] = np.flip(order[above_threshold]).tolist()
+        order = order[~above_threshold]
 
     return keep_to_merge_list