Implements Chaikin corners rounding algorithm on ordered set of points

UIBezierPath+Chaikin.swift

import UIKit

extension UIBezierPath {
    private static func midpoint(_ a: CGPoint, b: CGPoint) -> CGPoint {
        CGPoint(
            x: (b.x + a.x) / 2,
            y: (b.y + a.y) / 2
        )
    }
    
    static func chaikinPath(_ pts: [CGPoint]) -> UIBezierPath? {
        guard pts.count > 2 else {
          return nil 
        }
        
        let path = UIBezierPath()
        for i in 1...pts.count {
            let prev = pts[i-1]
            let cp = pts[i % pts.count]
            let next = pts[(i + 1) % pts.count]
            
            path.move(
                to: midpoint(prev, b: cp)
            )
            path.addQuadCurve(
                to: midpoint(cp, b: next),
                controlPoint: cp
            )
        }
        path.close()
        return path
    }
}