Smooth drawing app for watchOS 3 written in Swift 3

This app uses the new WatchKit class, WKPanGestureRecognizer, to track finger movement and paints a random color stroke. The line is a UIBezierPath. It gets smoothed by addQuadCurve(to:controlPoint). The algotrighm accounts for the delay in the pan gesture recognizer by creating a backward projection of the stroke using the velocity of the gesture. It also creates a forward projection to stroke precisely under the user's finger. The app captures the drawing with UIGraphicsGetImageFromCurrentImageContext and uses that image for the background of a WKInterfaceGroup.

Device screenshot	Movie