Create gradients and cache them to reduce memory footprint.

GradientView.swift

class GradientView: UIImageView {
	
	var gradientColors: [CGColor] = [UIColor.greyishBrown.withAlphaComponent(0.2).cgColor, UIColor.greyishBrown.cgColor]
	var locations: [CGFloat]? = [0.0, 1.0]
	
	override func layoutSubviews() {
		self.contentMode = .scaleToFill
		self.backgroundColor = .hotPink
		self.image = drawGradientColor(in: self.bounds, colors: gradientColors)
	}
	
	func drawGradientColor(in rect: CGRect, colors: [CGColor]) -> UIImage? {
		let currentContext = UIGraphicsGetCurrentContext()
		currentContext?.saveGState()
		defer { currentContext?.restoreGState() }
		
		let size = rect.size
		UIGraphicsBeginImageContextWithOptions(size, false, 0)
		guard let gradient = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(),
										colors: colors as CFArray,
										locations: locations) else { return nil }
		
		let context = UIGraphicsGetCurrentContext()
		context?.drawLinearGradient(gradient,
									start: CGPoint.zero,
									end: CGPoint(x: size.width, y: 0),
									options: [])
		let gradientImage = UIGraphicsGetImageFromCurrentImageContext()
		UIGraphicsEndImageContext()
		return gradientImage
	}
}