Add backward compatibility for older opencv versions

Author: arunponnusamy

Diff for: yolo_opencv.py

@@ -24,8 +24,10 @@
 def get_output_layers(net):
 
     layer_names = net.getLayerNames()
-    
-    output_layers = [layer_names[i - 1] for i in net.getUnconnectedOutLayers()]
+    try:
+        output_layers = [layer_names[i - 1] for i in net.getUnconnectedOutLayers()]
+    except:
+        output_layers = [layer_names[i[0] - 1] for i in net.getUnconnectedOutLayers()]
 
     return output_layers
 
@@ -89,7 +91,12 @@ def draw_prediction(img, class_id, confidence, x, y, x_plus_w, y_plus_h):
 indices = cv2.dnn.NMSBoxes(boxes, confidences, conf_threshold, nms_threshold)
 
 for i in indices:
-    box = boxes[i]
+    try:
+        box = boxes[i]
+    except:
+        i = i[0]
+        box = boxes[i]
+    
     x = box[0]
     y = box[1]
     w = box[2]