[英]Draw a line realtime with Swift 3.0
我试图在UIImageView上绘图。 使用Swift 1.2我能够让它工作,但我不得不将它转换为swift 3.0而我无法让它工作。
它需要做的是用手指准确地绘制你在屏幕上绘制的内容。
代码没有错误,但只是没有显示任何内容。
变量;
var lastPoint = CGPoint.zero
var red: CGFloat = 0.0
var green: CGFloat = 0.0
var blue: CGFloat = 0.0
var brushWidth: CGFloat = 10.0
var opacity: CGFloat = 1.0
var swiped = false
编码;
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
swiped = false
if let touch = touches.first {
lastPoint = touch.location(in: self.view)
}
}
func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint) {
imageView.image?.draw(in: CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height))
UIGraphicsBeginImageContext(self.imageView.bounds.size);
let context = UIGraphicsGetCurrentContext()
context?.move(to: fromPoint)
context?.addLine(to: toPoint)
context?.setLineCap(CGLineCap.round)
context?.setLineWidth(brushWidth)
context?.setStrokeColor(red: red, green: green, blue: blue, alpha: 1.0)
context?.setBlendMode(CGBlendMode.normal)
imageView.image = UIGraphicsGetImageFromCurrentImageContext()
imageView.alpha = opacity
UIGraphicsEndImageContext()
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
swiped = true
if let touch = touches.first {
let currentPoint = touch.location(in: view)
drawLineFrom(fromPoint: lastPoint, toPoint: currentPoint)
lastPoint = currentPoint
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
if !swiped {
// draw a single point
self.drawLineFrom(fromPoint: lastPoint, toPoint: lastPoint)
}
你必须开始图像上下文:
UIGraphicsBeginImageContextWithOptions(view.bounds.size, false, 0)
你还必须克服这条道路:
context?.strokePath()
您也没有绘制上一张图片:
imageView.image?.draw(in: view.bounds)
从而:
func drawLine(from fromPoint: CGPoint, to toPoint: CGPoint) {
UIGraphicsBeginImageContextWithOptions(view.bounds.size, false, 0)
imageView.image?.draw(in: view.bounds)
let context = UIGraphicsGetCurrentContext()
context?.move(to: fromPoint)
context?.addLine(to: toPoint)
context?.setLineCap(CGLineCap.round)
context?.setLineWidth(brushWidth)
context?.setStrokeColor(red: red, green: green, blue: blue, alpha: 1.0)
context?.setBlendMode(CGBlendMode.normal)
context?.strokePath()
imageView.image = UIGraphicsGetImageFromCurrentImageContext()
imageView.alpha = opacity
UIGraphicsEndImageContext()
}
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