title: Is it possible to hide my app's view in screenshot?
body: <p>Is it possible to hide or blur the whole screen or part of the screen of my app when the user is taking a screenshot as of iOS 11? If I could get the event <em>before</em> the capture I would be able to hide the view, but according to my research, there is an event only <em>after</em> the capture.</p>
  
  <p>All StackOverflow and Google search results say preventing screenshot is impossible, but since I had seen an app that did that (though I am not sure it still works on iOS 11), I cannot easily tell the client it is impossible.</p>
  
  <p>When I had an iPad (iOS 10), I could not capture the screen of one Bitcoin wallet app. I tried to save its recovery key screen, but the screenshot image was blurred or something (I cannot remember exactly). I think the app's name was Bread. Unfortunately, right now, I do not have an iOS device, so I cannot test it. </p>
  
  <p>How did the app do it? Did the app modify the captured image after the screenshot event? Is it possible to modify the screenshot silently?</p>