title: Flutter: display photo or image as modal popup
body: <p>I'm trying to find a solution to have in flutter kind of modal dialog coming up, like an overlay widget over the screen. </p>
  
  <p>Use case: I have a user photo shown as small circle avatar image. If the user taps on the photo, a "popup" shall overlay the screen allowing the user to see the full size photo. For example with the package "photo_view package". Any idea how to solve this? I cannot add the photo_view widget directly to the scaffold as it would permanently overlay the screen. I need it only when tapping on the mini icon. </p>
  
  <p>Thanks!</p>