SKTexture+Gradient.swift

extension SKTexture
{
  convenience init(radialGradientWithColors colors: [UIColor], locations: [CGFloat], size: CGSize)
  {
    let renderer = UIGraphicsImageRenderer(size: size)
    let image = renderer.image { (context) in
      let colorSpace = context.cgContext.colorSpace ?? CGColorSpaceCreateDeviceRGB()
      let cgColors = colors.map({ $0.cgColor }) as CFArray
      guard let gradient = CGGradient(colorsSpace: colorSpace, colors: cgColors, locations: UnsafePointer<CGFloat>(locations)) else {
                fatalError("Failed creating gradient.")
      }
            
      let radius = max(size.width, size.height) / 2.0
      let midPoint = CGPoint(x: size.width / 2.0, y: size.height / 2.0)
      context.cgContext.drawRadialGradient(gradient, startCenter: midPoint, startRadius: 0, endCenter: midPoint, endRadius: radius, options: [])
    }
        
    self.init(image: image)
  }
    
    
  convenience init(linearGradientWithAngle angleInRadians: CGFloat, colors: [UIColor], locations: [CGFloat], size: CGSize)
  {
    let renderer = UIGraphicsImageRenderer(size: size)
    let image = renderer.image { (context) in
      let colorSpace = context.cgContext.colorSpace ?? CGColorSpaceCreateDeviceRGB()
      let cgColors = colors.map({ $0.cgColor }) as CFArray
      guard let gradient = CGGradient(colorsSpace: colorSpace, colors: cgColors, locations: UnsafePointer<CGFloat>(locations)) else {
                fatalError("Failed creating gradient.")
      }
            
      let angles = [angleInRadians + .pi, angleInRadians]
      let radius = (pow(size.width / 2.0, 2.0) + pow(size.height / 2.0, 2.0)).squareRoot()
      let points = angles.map { (angle) -> CGPoint in
        let dx = radius * cos(-angle) + size.width / 2.0
        let dy = radius * sin(-angle) + size.height / 2.0
        return CGPoint(x: dx, y: dy)
      }
            
      context.cgContext.drawLinearGradient(gradient, start: points[0], end: points[1], options: [])
    }
        
    self.init(image: image)
  }
}