Apply perpective transform to the Vision rectangle observation

perspectiveForRectangle.swift

guard let rectangle = request?.results?.first as? VNRectangleObservation else {
    guard let error = error else { return }
    print("Error: Rectangle detection failed - Vision request returned an error. \(error.localizedDescription)")
    return
}
guard let filter = CIFilter(name: "CIPerspectiveCorrection") else {
    print("Error: Rectangle detection failed - Could not create perspective correction filter.")
    return
}
let width = CGFloat(CVPixelBufferGetWidth(currentCameraImage))
let height = CGFloat(CVPixelBufferGetHeight(currentCameraImage))
let topLeft = CGPoint(x: rectangle.topLeft.x * width, y: rectangle.topLeft.y * height)
let topRight = CGPoint(x: rectangle.topRight.x * width, y: rectangle.topRight.y * height)
let bottomLeft = CGPoint(x: rectangle.bottomLeft.x * width, y: rectangle.bottomLeft.y * height)
let bottomRight = CGPoint(x: rectangle.bottomRight.x * width, y: rectangle.bottomRight.y * height)

filter.setValue(CIVector(cgPoint: topLeft), forKey: "inputTopLeft")
filter.setValue(CIVector(cgPoint: topRight), forKey: "inputTopRight")
filter.setValue(CIVector(cgPoint: bottomLeft), forKey: "inputBottomLeft")
filter.setValue(CIVector(cgPoint: bottomRight), forKey: "inputBottomRight")

let ciImage = CIImage(cvPixelBuffer: currentCameraImage).oriented(.up)
filter.setValue(ciImage, forKey: kCIInputImageKey)

guard let perspectiveImage: CIImage = filter.value(forKey: kCIOutputImageKey) as? CIImage else {
    print("Error: Rectangle detection failed - perspective correction filter has no output image.")
    return
}
delegate?.rectangleFound(rectangleContent: perspectiveImage)