@IBOutlet weak var scanAreaImage: UIImageView!
var regionOfInterest: CGRect!

let someRect: CGRect = scanAreaImage.frame
        regionOfInterest = someRect

func highlightLetters(box: VNRectangleObservation) {

    let xCord = box.topLeft.x * (cameraPreviewlayer?.frame.size.width)!
    let yCord = (1 - box.topLeft.y) * (cameraPreviewlayer?.frame.size.height)!
    let width = (box.topRight.x - box.bottomLeft.x) * (cameraPreviewlayer?.frame.size.width)!
    let height = (box.topLeft.y - box.bottomLeft.y) * (cameraPreviewlayer?.frame.size.height)!

// This is the section I Added for the rec of interest detection zone.
//////////////////////////////////////////////

    let wordRect = CGRect(x: xCord, y: yCord, width: width, height: height)
    guard regionOfInterest.contains(wordRect.origin) else { return } // only draw a box if the orgin of the word box is within the regionOfInterest

// regionOfInterest being the cgRect you created earlier
   //////////////////////////////////////////////

    let outline = CALayer()
    outline.frame = CGRect(x: xCord, y: yCord, width: width, height: height)
    outline.borderWidth = 1.0
    if textColour == 1 {
        outline.borderColor = UIColor.blue.cgColor
    }else {
        outline.borderColor = UIColor.clear.cgColor
    }

    cameraPreviewlayer?.addSublayer(outline)