almaleh

class FreedrawingImageViewCG: UIImageView {
    
    var currentTouchPosition: CGPoint?
    
    override func layoutSubviews() {
        super.layoutSubviews()
        isUserInteractionEnabled = true
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

almaleh

class FreedrawingView: UIView {
    
    // we use a multi-dimensional array to store separate lines, otherwise 
    // all your lines will be connected
    var lines = [[CGPoint]]()
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        // create a new line
        lines.append([CGPoint]())
    }

almaleh

func calculateRectBetween(lastPoint: CGPoint, newPoint: CGPoint) -> CGRect {
    let originX = min(lastPoint.x, newPoint.x) - (lineWidth / 2)
    let originY = min(lastPoint.y, newPoint.y) - (lineWidth / 2)

    let maxX = max(lastPoint.x, newPoint.x) + (lineWidth / 2)
    let maxY = max(lastPoint.y, newPoint.y) + (lineWidth / 2)

    let width = maxX - originX
    let height = maxY - originY

almaleh

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    guard let newTouchPoint = touches.first?.location(in: self) else { return }

    var lastTouchPoint: CGPoint = .zero

    if let lastIndex = lines.indices.last {
        // get reference to last point
        if let lastPoint = lines[lastIndex].last { lastTouchPoint = lastPoint }

        // add new point

almaleh

var flattenedImage: UIImage?
var line = [CGPoint]() {
    didSet {
        checkIfTooManyPointsIn(&line)
    }
}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    flattenImage()

almaleh

    override func draw(_ rect: CGRect) {
        super.draw(rect)
        guard let context = UIGraphicsGetCurrentContext() else { return }
        
        // draw the flattened image if it exists
        if let image = flattenedImage {
            image.draw(in: self.bounds)
        }
        
        context.setStrokeColor(lineColor.cgColor)

almaleh

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    guard let newTouchPoint = touches.first?.location(in: self) else { return }

    let lastTouchPoint: CGPoint = line.last ?? .zero
    line.append(newTouchPoint)
    let rect = calculateRectBetween(lastPoint: lastTouchPoint, newPoint: newTouchPoint)
    layer.setNeedsDisplay(rect)
}

almaleh

  override func draw(_ layer: CALayer, in ctx: CGContext) {
      // 1
      let drawingLayer = self.drawingLayer ?? CAShapeLayer()
      // 2
      drawingLayer.contentsScale = UIScreen.main.scale
      // 3
      let linePath = UIBezierPath()
      // 4
      for (index, point) in line.enumerated() {
          if index == 0 {

almaleh

  func checkIfTooManyPoints() {
      let maxPoints = 25
      if line.count > maxPoints {
          updateFlattenedLayer()
          // we leave two points to ensure no gaps or sharp angles
          _ = line.removeFirst(maxPoints - 2)
      }
  }

almaleh

func updateFlattenedLayer() {
    // 1
    guard let drawingLayer = drawingLayer,
        // 2
        let optionalDrawing = try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(
            NSKeyedArchiver.archivedData(withRootObject: drawingLayer, requiringSecureCoding: false))
            as? CAShapeLayer,
        // 3
        let newDrawing = optionalDrawing else { return }
    // 4