title: Vertical Alpha Gradient without the use of color in iOS
body: <p>I have an app that uses the back camera's output as it's background. I also have a UITableView or UIScrollView (depending on the ViewController) on top of the camera view. I want to add a top-bar menu. This menu should not have any of the content of the UITableView or UIScrollView underneath it. To make it look nice I want the UITableView and UIScrollView to fade out on a gradient ... 255 (1.0f) alpha all the way up until ~45 pixels away from reaching the top-bar menu view. I have tried many "solutions" but all of them assume that the background color you want to fade too is known, in this case the background color is actually a video (of sorts). The real question here is: <strong>is there a way with iOS to have an alpha only gradient on a view... even if the view below it is a dynamically changing image?</strong> This solution <em>cannot</em> include ANY image manipulation, because the "image" is actually the back camera output and processing the image will take too much time and ultimately slow down the app.</p>
  
  <p>Thank you in advance for anyone willing to answer my question... if it is simply not possible please explain why and I will be willing to mark your answer as correct.</p>
  
  <p>any code can be in Objective-C or Swift (Swift is preferred)</p>
  
  <p>iOS 8 is the target OS in this app, so if any iOS 8 libraries can help solve this question feel free to use it.</p>