locationdetection.swift

func drawStroke(context: CGContext?, touch: UITouch) {
    let location = touch.location(in: self)
    if touch.type == .stylus {
        minX = min(minX, Int(location.x))
        minY = min(minY, Int(location.y))
        maxX = max(maxX, Int(location.x))
        maxY = max(maxY, Int(location.y))
        //....
    }
    //....
}

public func setup () {   
    trackTimer = Timer.scheduledTimer(withTimeInterval: 0.5, repeats: true, block: { 
        timer in
        //user pauses for more than a second when drawing
        //let's draw a border around it and save the area to an uiimage                                                                            
        let now = Date().timeIntervalSince1970
        if Int(self.lastTouchTimestamp!) > 0 && now - self.lastTouchTimestamp! > 1 {
            self.drawDoodlingRect(context: self.context)
        }
    })  
}

func drawDoodlingRect(context: CGContext?) {
    let inset = 5
        
    ocrImageRect = CGRect(x: minX - inset, 
                          y: minY - inset, 
                          width: (maxX-minX) + inset*2, 
                          height: (maxY-minY) + 2*inset)
        
    context!.strokePath()
        
    //...
        
    fetchOCRText()
}

func fetchOCRText () {
    let ocrImage = image!.crop(rect: ocrImageRect!)
    
    switch recognizeMode {
        case .cognitiveServiceOCR:
            recognizeWithCognitiveServiceOCR(ocrImage)
        case .localMLModel:
            recognizeWithLocalModel(ocrImage)
            break
    }
}