title: how to resize frame from video and then retrieve the final size?
body: <p>I want to read a video file, break it into separate frames, resize each frame to a max width and then retrieve width and height of final image.</p>
  
  <p>I've tried this:</p>
  
  <p>while True:</p>
  
  <pre><code>vs = cv2.VideoCapture(args["video"])
  # grab the frame from the threaded video stream and resize it
  # to have a maximum width of 400 pixels
  frame = vs.read()
  frame = imutils.resize(frame, width=400)
  
  # grab the frame dimensions and convert it to a blob
  w, h = cv.GetSize(frame)
  </code></pre>
  
  <p>but am getting:</p>
  
  <pre><code>Traceback (most recent call last):
    File "real_time_object_detection.py", line 52, in &lt;module&gt;
      frame = imutils.resize(frame, width=400)
    File "/home/pi/.virtualenvs/cv/lib/python3.5/site-packages/imutils/convenience.py", line 69, in resize
      (h, w) = image.shape[:2]
  AttributeError: 'tuple' object has no attribute 'shape'
  </code></pre>
  
  <p>why does it complain about a line in <code>imutils/</code>? How can I do the required?</p>