Switched overlap to IoU.

imutils/object_detection.py

@@ -1,7 +1,7 @@
 # import the necessary packages
 import numpy as np
 
-def non_max_suppression(boxes, probs=None, overlapThresh=0.3):
+def non_max_suppression(boxes, probs=None, iouThresh=0.3):
 	# if there are no boxes, return an empty list
 	if len(boxes) == 0:
 		return []
@@ -53,13 +53,15 @@ def non_max_suppression(boxes, probs=None, overlapThresh=0.3):
 		w = np.maximum(0, xx2 - xx1 + 1)
 		h = np.maximum(0, yy2 - yy1 + 1)
 
-		# compute the ratio of overlap
-		overlap = (w * h) / area[idxs[:last]]
+		# compute the IoU
+		intersections = w * h
+              IoU = intersections / (area[idxs[:last]] + area[i] - intersections)
 
 		# delete all indexes from the index list that have overlap greater
 		# than the provided overlap threshold
 		idxs = np.delete(idxs, np.concatenate(([last],
-			np.where(overlap > overlapThresh)[0])))
+			np.where(IoU > iouThresh)[0])))
 
 	# return only the bounding boxes that were picked
-	return boxes[pick].astype("int")
+	return boxes[pick].astype("int")
+