Vision-Image-Perspective-Correction.swift

func doPerspectiveCorrection(_ observation: VNRectangleObservation, from buffer: CVImageBuffer) {

        var ciImage = CIImage(cvImageBuffer: buffer)

        let topLeft = observation.topLeft.scaled(to: ciImage.extent.size)
        let topRight = observation.topRight.scaled(to: ciImage.extent.size)
        let bottomLeft = observation.bottomLeft.scaled(to: ciImage.extent.size)
        let bottomRight = observation.bottomRight.scaled(to: ciImage.extent.size)

        ciImage = ciImage.applyingFilter("CIPerspectiveCorrection", parameters: [
            "inputTopLeft": CIVector(cgPoint: topLeft),
            "inputTopRight": CIVector(cgPoint: topRight),
            "inputBottomLeft": CIVector(cgPoint: bottomLeft),
            "inputBottomRight": CIVector(cgPoint: bottomRight),
        ])

        let context = CIContext()
        let cgImage = context.createCGImage(ciImage, from: ciImage.extent)
        let output = UIImage(cgImage: cgImage!)
        
        UIImageWriteToSavedPhotosAlbum(output, nil, nil, nil)
        
}