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Slow CPU-based Drawing
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class FreedrawingImageViewCG: UIImageView { | |
var currentTouchPosition: CGPoint? | |
override func layoutSubviews() { | |
super.layoutSubviews() | |
isUserInteractionEnabled = true | |
} | |
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { | |
super.touchesBegan(touches, with: event) | |
guard let newTouchPoint = touches.first?.location(in: self) else { return } | |
currentTouchPosition = newTouchPoint | |
} | |
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) { | |
guard let newTouchPoint = touches.first?.location(in: self) else { return } | |
guard let previousTouchPoint = currentTouchPosition else { return } | |
let renderer = UIGraphicsImageRenderer(size: bounds.size) | |
image = renderer.image { ctx in | |
image?.draw(in: bounds) | |
UIColor.red.setStroke() | |
ctx.cgContext.setLineCap(.round) | |
ctx.cgContext.setLineWidth(5) | |
ctx.cgContext.move(to: previousTouchPoint) | |
ctx.cgContext.addLine(to: newTouchPoint) | |
ctx.cgContext.strokePath() | |
} | |
currentTouchPosition = newTouchPoint | |
} | |
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) { | |
currentTouchPosition = nil | |
} | |
} |
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