Fade out scrolling UITextView over image?

I’m looking to fade out a scrolling UITextView over a background image, something similar to the gradient at the top of this little example.

I’m trying to work out how I can achieve this using CAGradientLayer and masks. As the text in the view scrolls (vertically), I need the text to become transparent before it hits the frame of the view, to give the illusion that it’s fading out upward and downward.

Any tips on how I might achieve this?

Oh man, I use this a lot. Have it saved as a snippet:

CAGradientLayer *gradient = [CAGradientLayer layer];

gradient.frame = self.textView.superview.bounds;
gradient.colors = @[(id)[UIColor clearColor].CGColor, (id)[UIColor blackColor].CGColor, (id)[UIColor blackColor].CGColor, (id)[UIColor clearColor].CGColor];
gradient.locations = @[@0.0, @0.03, @0.97, @1.0];

self.textView.superview.layer.mask = gradient;

This solution requires that your text view be embedded in a view of its own. This applies a 3% fade to the top and bottom of the text view. Modify gradient.locations to your needs.

I've been inspired by others from this thread, but have converted the code to Swift and used start and end point instead, to make a gradient at the bottom.

if let containerView = textView.superview {
    let gradient = CAGradientLayer(layer: containerView.layer)
    gradient.frame = containerView.bounds
    gradient.colors = [UIColor.clearColor().CGColor, UIColor.blueColor().CGColor]
    gradient.startPoint = CGPoint(x: 0.0, y: 1.0)
    gradient.endPoint = CGPoint(x: 0.0, y: 0.85)
    containerView.layer.mask = gradient
    }

See: image of textView bottom with gradient