title: How to count objects in Tensorflow Object Detection API
body: <p>I am executing <a href="https://github.com/tensorflow/tensorflow" rel="noreferrer">https://github.com/tensorflow/tensorflow</a> this example of detecting objects in image.</p>
  
  <p>I want to get count of detected objects following is the code that gives me detected object drawn in an image. But I am not able to get count of detected objects.</p>
  
  <pre><code>with detection_graph.as_default():
  with tf.Session(graph=detection_graph) as sess:
      for image_path in TEST_IMAGE_PATHS:
        image = Image.open(image_path)
        # the array based representation of the image will be used later in order to prepare the
        # result image with boxes and labels on it.
        image_np = load_image_into_numpy_array(image)
        # Expand dimensions since the model expects images to have shape: [1, None, None, 3]
        image_np_expanded = np.expand_dims(image_np, axis=0)
        image_tensor = detection_graph.get_tensor_by_name('image_tensor:0')
        # Each box represents a part of the image where a particular object was detected.
        boxes = detection_graph.get_tensor_by_name('detection_boxes:0')
        # Each score represent how level of confidence for each of the objects.
        # Score is shown on the result image, together with the class label.
        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')
        # Actual detection.
        (boxes, scores, classes, num_detections) = sess.run(
            [boxes, scores, classes, num_detections],
            feed_dict={image_tensor: image_np_expanded})
        # Visualization of the results of a detection.
        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)
        plt.figure(figsize=IMAGE_SIZE)
        plt.imshow(image_np)
  </code></pre>
  
  <p>This is the block of code that gives actual object detection shown in below image:</p>
  
  <p><a href="https://i.stack.imgur.com/XKqLE.png" rel="noreferrer"><img src="https://i.stack.imgur.com/XKqLE.png" alt="enter image description here"></a></p>
  
  <p>How can I get the object count?</p>