title: How can I add zoom in/out gesture in Android vision CameraSource
body: <p>I'm trying to develop a simple camera app with face detection and i'm using android-vision sample from here 
  <a href="https://github.com/googlesamples/android-vision/tree/master/visionSamples/FaceTracker" rel="noreferrer">https://github.com/googlesamples/android-vision/tree/master/visionSamples/FaceTracker</a></p>
  
  <p>Everything is working fine and i need to add zoom in/out feature in it. I searched SO but found nothing related to vision. Every answer is related to Camera2.</p>