绘图应用程序快速，性能缓慢和低FPS

Question

>我正在尝试创建一个绘图应用程序，使用此代码绘制线条，但它的性能非常慢

func drawLineNew(_ prevPoint1 : CGPoint,_ prevPoint2 : CGPoint ,_ currentPoint : CGPoint){
UIGraphicsBeginImageContextWithOptions(ImageView.frame.size, false, 0.0)
let context = UIGraphicsGetCurrentContext()
ImageView.image?.draw(in: CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height))
var mid1 = CGPoint.init(x: (prevPoint1.x + prevPoint2.x)*0.5, y: (prevPoint1.y + prevPoint2.y)*0.5)
var mid2 = CGPoint.init(x: ((currentPoint.x) + prevPoint1.x)*0.5, y: ((currentPoint.y) + prevPoint1.y)*0.5)
context?.move(to: prevPoint2)
context?.addCurve(to: mid2, control1: mid1, control2: prevPoint1)
context?.setLineCap(CGLineCap.round)
context?.setLineWidth(brushWidth)
context?.setStrokeColor(red: red, green: green, blue: blue, alpha: opacity)
context?.setBlendMode(CGBlendMode.normal )
//context?.setShouldAntialias(true)
context?.strokePath()
ImageView.image = UIGraphicsGetImageFromCurrentImageContext()
ImageView.alpha = 1.0
self.prevPoint1 = mid2
//context?.clear(CGRect.init(origin: CGPoint.init(x: 0, y: 0), size: ImageView.frame.size))
UIGraphicsEndImageContext()
lastPoint = currentPoint
}

Answer 1

绘制太多线条时性能会变慢。考虑通过不根据绘图区域的大小以及像素在显示比例上表示的距离绘制所有线条来优化性能。