Swift 3 Add custom annotation pin to MKMapSnapShotter snapshot

To render a MKMapSnapshot with annotation views, you have to manually draw the snapshot's image and the annotation view's image on a new graphic context, and get a new image from that context. In Swift 3:

let rect = imageView.bounds

let snapshot = MKMapSnapshotter(options: options)
snapshot.start { snapshot, error in
    guard let snapshot = snapshot, error == nil else {
        print(error ?? "Unknown error")
        return
    }

    let image = UIGraphicsImageRenderer(size: options.size).image { _ in
        snapshot.image.draw(at: .zero)

        let pinView = MKPinAnnotationView(annotation: nil, reuseIdentifier: nil)
        let pinImage = pinView.image

        var point = snapshot.point(for: location.coordinate)

        if rect.contains(point) {
            point.x -= pinView.bounds.width / 2
            point.y -= pinView.bounds.height / 2
            point.x += pinView.centerOffset.x
            point.y += pinView.centerOffset.y
            pinImage?.draw(at: point)
        }
    }

    // do whatever you want with this image, e.g.

    DispatchQueue.main.async {
        imageView.image = image
    }
}

This was adapted from https://stackoverflow.com/a/18776723/1271826, which itself was adapted from WWDC 2013 video Putting MapKit in Perspective.

Here is an example of a snapshot with a .satelliteFlyover: