我怎样才能让这个签名视图更清晰，更少模糊？

当用户在其上绘图时，如何制作应具有最佳清晰度的签名视图。我使用此代码使用CoreGraphics. 目前它是这样的，我想要另一个。帮我解决这个问题。下面是代码片段。

我得到像这个链接的图像

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我希望图像更清晰，就像这个链接

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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()
    }
}