stroked path playground

StrokedPath.swift

import UIKit
import ImageIO
import MobileCoreServices
import PlaygroundSupport

let documentFolderUrl = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
print(documentFolderUrl)

class ShapeView: UIView {
    override class var layerClass: AnyClass { return CAShapeLayer.self }
    private(set) lazy var shapeLayer: CAShapeLayer = { self.layer as! CAShapeLayer }()

    init(frame: CGRect, path: CGPath) {
        super.init(frame: frame)
        shapeLayer.path = path
        shapeLayer.lineCap = kCALineCapButt
        shapeLayer.lineJoin = kCALineJoinRound
        shapeLayer.lineWidth = 1
        shapeLayer.fillColor = nil
        shapeLayer.strokeColor = nil
    }

    required init?(coder decoder: NSCoder) { fatalError() }
}

extension UIView {
    var snapshotImage: UIImage {
        let format = UIGraphicsImageRendererFormat.default()
        format.scale = 1
        return UIGraphicsImageRenderer(bounds: bounds, format: format).image { rc in
            drawHierarchy(in: bounds, afterScreenUpdates: true)
        }
    }

    func savePng(to filename: String) {
        try! UIImagePNGRepresentation(snapshotImage)!.write(to: documentFolderUrl.appendingPathComponent(filename), options: .atomic)
    }
}

func saveAnimatedGif(to filename: String, frameCount: Int, frameFunction: (_ frameNumber: Int, _ frameCount: Int) -> UIImage) {
    let fileGifProperties: [CFString: Any] = [kCGImagePropertyGIFLoopCount: NSNumber(value: UInt16(0))]
    let fileProperties: [CFString: Any] = [kCGImagePropertyGIFDictionary: fileGifProperties]
    let frameGifProperties: [CFString: Any] = [kCGImagePropertyGIFDelayTime: NSNumber(value: Float(1) / 30)]
    let frameProperties: [CFString: Any] = [kCGImagePropertyGIFDictionary: frameGifProperties]
    let destination = CGImageDestinationCreateWithURL(documentFolderUrl.appendingPathComponent(filename) as CFURL, kUTTypeGIF, frameCount, fileProperties as CFDictionary)!

    for i in 0 ..< frameCount {
        CGImageDestinationAddImage(destination, frameFunction(i, frameCount).cgImage!, frameProperties as CFDictionary)
    }

//    CGImageDestinationSetProperties(destination, fileProperties as CFDictionary)
    CGImageDestinationFinalize(destination)
}

let rootView = UIView(frame: CGRect(x: 0, y: 0, width: 400, height: 150))
rootView.backgroundColor = .white

let corePath = CGMutablePath()
let rect = rootView.bounds.insetBy(dx: 20, dy: 20)
corePath.addLines(between: [
    CGPoint(x: rect.minX, y: rect.minY),
    CGPoint(x: rect.midX - 2, y: rect.maxY),
    CGPoint(x: rect.midX + 2, y: rect.maxY),
    CGPoint(x: rect.maxX, y: rect.minY)])

let corePathView = ShapeView(frame: rootView.bounds, path: corePath)
corePathView.shapeLayer.strokeColor = UIColor(hue: 0, saturation: 0.9, brightness: 0.9, alpha: 1).cgColor
corePathView.savePng(to: "corePathView.png")
rootView.addSubview(corePathView)

let strokeView = ShapeView(frame: rootView.bounds, path: corePath)
strokeView.shapeLayer.strokeColor = UIColor(hue: 0, saturation: 0.4, brightness: 1.0, alpha: 1).cgColor
strokeView.shapeLayer.lineWidth = 40
strokeView.shapeLayer.lineJoin = kCALineJoinBevel
strokeView.savePng(to: "strokeView.png")
rootView.insertSubview(strokeView, belowSubview: corePathView)

let strokedCopyPath = corePath.copy(strokingWithWidth: strokeView.shapeLayer.lineWidth, lineCap: .butt, lineJoin: .bevel, miterLimit: 0)
let strokedCopyView = ShapeView(frame: rootView.bounds, path: strokedCopyPath)
strokedCopyView.shapeLayer.strokeColor = UIColor(hue: 0, saturation: 0.6, brightness: 0.6, alpha: 1).cgColor
strokedCopyView.shapeLayer.lineJoin = kCALineJoinRound
strokedCopyView.shapeLayer.lineWidth = 1
strokedCopyView.shapeLayer.miterLimit = 20
strokedCopyView.savePng(to: "strokedCopyView.png")
rootView.addSubview(strokedCopyView)

let thinStrokedCopyPath = corePath.copy(strokingWithWidth: 8, lineCap: .butt, lineJoin: .bevel, miterLimit: 0)
let thinStrokedCopyView = ShapeView(frame: rootView.bounds, path: thinStrokedCopyPath)
thinStrokedCopyView.shapeLayer.strokeColor = UIColor(hue: 0, saturation: 0.6, brightness: 0.6, alpha: 1).cgColor
thinStrokedCopyView.shapeLayer.lineJoin = kCALineJoinBevel
thinStrokedCopyView.shapeLayer.lineWidth = 2
thinStrokedCopyView.shapeLayer.miterLimit = 20
thinStrokedCopyView.savePng(to: "thinStrokedCopyView.png")

if false {
    strokedCopyView.backgroundColor = .white
    saveAnimatedGif(to: "animatedStrokeCopy.gif", frameCount: 201) { (frameNumber: Int, frameCount: Int) in
        strokedCopyView.shapeLayer.strokeStart = CGFloat(frameCount - frameNumber) / CGFloat(frameCount - 1)
        return strokedCopyView.snapshotImage
    }
    strokedCopyView.backgroundColor = nil
    strokedCopyView.shapeLayer.strokeStart = 0
}

PlaygroundPage.current.liveView = rootView

For https://stackoverflow.com/a/45135864/77567