public class Vignette: BasicOperation {
    public var center: Position = Position.center { didSet { uniformSettings["vignetteCenter"] = center } }
    public var color: Color = Color.black { didSet { uniformSettings["vignetteColor"] = color } }
    public var start: Float = 0.3 { didSet { uniformSettings["vignetteStart"] = start } }
    public var end: Float = 0.75 { didSet { uniformSettings["vignetteEnd"] = end } }

    public init() {
        super.init(fragmentShader: VignetteFragmentShader, numberOfInputs: 1)

        ({ center = Position.center })()
        ({ color = Color.black })()
        ({ start = 0.3 })()
        ({ end = 0.75 })()
    }
}
