title: swift - speed improvement in UIView pixel per pixel drawing
body: <p>is there a way to improve the speed / performance of drawing pixel per pixel into a UIView?</p>
  
  <p>The current implementation of a 500x500 pixel UIView, is terribly slow.</p>
  
  <pre><code>class CustomView: UIView {
  
  public var context = UIGraphicsGetCurrentContext()
  
  public var redvalues = [[CGFloat]](repeating: [CGFloat](repeating: 1.0, count: 500), count: 500)
  
  public var start = 0
  {
  didSet{
      self.setNeedsDisplay()
  }
  }
  
  override func draw(_ rect: CGRect
  {
  super.draw(rect)
  context = UIGraphicsGetCurrentContext()
  for yindex in 0...499{
      for xindex in 0...499 {
          context?.setStrokeColor(UIColor(red: redvalues[xindex][yindex], green: 0.0, blue: 0.0, alpha: 1.0).cgColor)
  
          context?.setLineWidth(2)
          context?.beginPath()
          context?.move(to: CGPoint(x: CGFloat(xindex), y: CGFloat(yindex)))
          context?.addLine(to: CGPoint(x: CGFloat(xindex)+1.0, y: CGFloat(yindex)))
          context?.strokePath()
      }
  }
  }
  }
  </code></pre>
  
  <p>Thank you very much</p>