title: Detect object in specific region of frame
body: <p>I would like to detect objects from the region of a frame using tensorflows object detection api. I have split the frame into region_1 and region_2 but how do I perform detection only in region_1 from the frame and draw rectangles only in region1</p>
  
  <pre><code>def detect_objects(image_np, sess, detection_graph):
  
      region_1 = image_np[zone1[1]: zone1[3], zone1[0]:zone1[2]]
      region_2 = image_np[zone2[1]: zone2[3], zone2[0]:zone2[2]]
  
      image_np_expanded = np.expand_dims(image_np, axis=0)
      image_tensor = detection_graph.get_tensor_by_name('image_tensor:0')
  
      boxes = detection_graph.get_tensor_by_name('detection_boxes:0')
  
      scores = detection_graph.get_tensor_by_name('detection_scores:0')
      classes = detection_graph.get_tensor_by_name('detection_classes:0')
      num_detections = detection_graph.get_tensor_by_name('num_detections:0')
  
      (boxes, scores, classes, num_detections) = sess.run(
          [boxes, scores, classes, num_detections],
          feed_dict={image_tensor: image_np_expanded})
  
      vis_util.visualize_boxes_and_labels_on_image_array(
          image_np,
          np.squeeze(boxes),
          np.squeeze(classes).astype(np.int32),
          np.squeeze(scores),
          category_index,
          use_normalized_coordinates=True,
          line_thickness=1)
      return image_np
  </code></pre>