How to draw a gradient line (fading in/out) with Core Graphics/iPhone?

Question

I know how to draw a simple line:

CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
CGContextMoveToPoint(context, x, y);
CGContextAddLineToPoint(conte         


        

Answer 1

I created a Swift version of Benjohn's answer.

class MyView: UIView {
    override func draw(_ rect: CGRect) {
    super.draw(rect)

    guard let context = UIGraphicsGetCurrentContext() else {
        return
    }

    context.addPath(createPath().cgPath)
    context.setLineWidth(15)
    context.replacePathWithStrokedPath()
    context.clip()

    let gradient = CGGradient(colorsSpace: nil, colors: [UIColor.red.cgColor, UIColor.yellow.cgColor, UIColor.green.cgColor] as CFArray, locations: [0, 0.4, 1.0])!
    let radius:CGFloat = 200
    let center = CGPoint(x: bounds.width / 2, y: bounds.height / 2)
    context.drawRadialGradient(gradient, startCenter: center, startRadius: 10, endCenter: center, endRadius: radius, options: .drawsBeforeStartLocation)
    }
}

If the createPath() method creates a triangle, you get something like this:

Hope this helps anyone!