How can i make this signature view more clear and less blur?

How can I make this signature view that should have optimal clarity when user drawing on it. I use this code to draw on image using CoreGraphics. Currently it coming like this and I want like another one. Help me with that. Below is the code snippet .

I am getting image like this link

.

I want image to more clear like this link

.

var lastPoint:CGPoint!
var isSwiping:Bool!
var isEditedImage = false
var lineWidth:CGFloat = 3.0
var lineOpacity:CGFloat = 1.0
var lineColor = UIColor.black

override func touchesBegan(_ touches: Set<UITouch>,
                          with event: UIEvent?){
    isSwiping    = false
    if let touch = touches.first{
        lastPoint = touch.location(in: signView)
    }
}

override func touchesMoved(_ touches: Set<UITouch>,
                           with event: UIEvent?){

    isSwiping = true
    if let touch = touches.first{
        let currentPoint = touch.location(in: signView)
        UIGraphicsBeginImageContext(self.signView.frame.size)
        self.signView.image?.draw(in: CGRect(x: 0, y: 0, width: self.signView.frame.size.width, height: self.signView.frame.size.height))
        UIGraphicsGetCurrentContext()?.move(to: CGPoint(x: lastPoint.x, y: lastPoint.y))
        UIGraphicsGetCurrentContext()?.addLine(to: CGPoint(x: currentPoint.x, y: currentPoint.y))
        UIGraphicsGetCurrentContext()?.setLineCap(CGLineCap.round)
        UIGraphicsGetCurrentContext()?.setLineWidth(lineWidth)
        UIGraphicsGetCurrentContext()?.setAlpha(lineOpacity)
        UIGraphicsGetCurrentContext()?.setStrokeColor(lineColor.cgColor)
        UIGraphicsGetCurrentContext()?.beginTransparencyLayer(auxiliaryInfo: nil)
        UIGraphicsGetCurrentContext()?.strokePath()
        UIGraphicsGetCurrentContext()?.endTransparencyLayer()
        self.signView.image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        lastPoint = currentPoint
        isEditedImage = true
    }
}

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

    if(!isSwiping) {
        // This is a single touch, draw a point
        UIGraphicsBeginImageContext(self.signView.frame.size)
        self.signView.image?.draw(in: CGRect(x: 0, y: 0, width: self.signView.frame.size.width, height: self.signView.frame.size.height))
        UIGraphicsGetCurrentContext()?.setLineCap(CGLineCap.round)
        UIGraphicsGetCurrentContext()?.setLineWidth(lineWidth)
        UIGraphicsGetCurrentContext()?.setAlpha(lineOpacity)
        UIGraphicsGetCurrentContext()?.setStrokeColor(lineColor.cgColor)
        UIGraphicsGetCurrentContext()?.beginTransparencyLayer(auxiliaryInfo: nil)
        UIGraphicsGetCurrentContext()?.strokePath()
        UIGraphicsGetCurrentContext()?.endTransparencyLayer()
        self.signView.image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
    }
}