title: Integrate OpenCV webcam into a Kivy user interface
body: <p>My current program is in Python and uses OpenCV. I rely on webcam captures and I am processing every captured frame:</p>
  
  <pre><code>import cv2
  
  # use the webcam
  cap = cv2.VideoCapture(0)
  while True:
      # read a frame from the webcam
      ret, img = cap.read()
      # transform image
  </code></pre>
  
  <p>I would like to make a Kivy interface (or another graphical user interface) with buttons, keeping already existing  functionality with webcam captures.</p>
  
  <p>I found this example: 
  <a href="https://kivy.org/docs/examples/gen__camera__main__py.html" rel="noreferrer">https://kivy.org/docs/examples/gen__camera__main__py.html</a> 
   — but it doesn’t explain how to acquire the webcam image to process it with OpenCV.</p>
  
  <p>I found an older example:
  <a href="http://thezestyblogfarmer.blogspot.it/2013/10/kivy-python-script-for-capturing.html" rel="noreferrer">http://thezestyblogfarmer.blogspot.it/2013/10/kivy-python-script-for-capturing.html</a>
  — it saves screenshots to disk using the ‘screenshot’ function. Then I can read the saved files and process them, but this seems to be an unnecessary step.</p>
  
  <p>What else can I try?</p>