将CIImage转换为UIImage会返回黑色图像

Question

我正在尝试使用核心图像和CIFilter来改变图像中的视角。但是在将CIImage转换为UIImage后，我的图像是黑色的。

    let perspectiveTransform = CIFilter(name: "CIPerspectiveTransform")!
    let composite = CIFilter(name: "CISourceAtopCompositing")!
    let backgroundImage = CIImage(image: UIImage(named: "interior0.jpg")!)!
    let clearImage = CIImage(image: UIImage(named: "clear.png")!)!
    perspectiveTransform.setValue(CIVector(x: CGFloat(perspectiveValues["inputTopLeftVectorX"]!), y: CGFloat(perspectiveValues["inputTopLeftVectorY"]!)),
                                  forKey: "inputTopLeft")
    perspectiveTransform.setValue(CIVector(x: CGFloat(perspectiveValues["inputTopRightVectorX"]!), y: CGFloat(perspectiveValues["inputTopRightVectorY"]!)),
                                  forKey: "inputTopRight")
    perspectiveTransform.setValue(CIVector(x: CGFloat(perspectiveValues["inputBottomRightVectorX"]!), y: CGFloat(perspectiveValues["inputBottomRightVectorY"]!)),
                                  forKey: "inputBottomRight")
    perspectiveTransform.setValue(CIVector(x: CGFloat(perspectiveValues["inputBottomLeftVectorX"]!), y: CGFloat(perspectiveValues["inputBottomLeftVectorY"]!)),
                                  forKey: "inputBottomLeft")
    perspectiveTransform.setValue(CIImage(image: (imageView?.image)!),
                                  forKey: kCIInputImageKey)

    let topImage = UIImage(CIImage: backgroundImage)

当我将topImage设置为imageView?.image时，它会显示黑色图像。 任何人都知道如何解决它？