Detect image colour from touch location - swift

Question

I am trying to build a simple drawing app that can act as a virtual guest book. Ive managed to put something simple together which allows a user to draw onto a UIImage however I cannot figure out a way to erase a drawing somebody creates without using the eraser function that I create as white. I would like to set an image however I need to figure out a way that the eraser can detect the correct colour to use based on where the users finger will be when erasing to match the image.
My eraser currently updates a set of variables (red, green, blue) the erasers function is #IBAction func eraser
I've tried a few functions that I've came across which are outdated
//
// SecondViewController.swift
// Guest Book
//
// Created by Stephen Clifford on 25/07/2019.
// Copyright © 2019 Stephen Clifford. All rights reserved.
//
import Foundation
import UIKit
class SecondViewController: UIViewController {
#IBOutlet weak var toolicon: UIButton!
#IBOutlet var imageView: UIImageView!
var lastPoint = CGPoint.zero
var swiped = false
var red:CGFloat = 0.00
var green:CGFloat = 0.00
var blue:CGFloat = 0.00
var alpha:CGFloat = 1
var lw:CGFloat = 2.5
var tool:UIImageView!
var isDrawing = true
override func viewDidLoad() {
super.viewDidLoad()
tool = UIImageView()
tool.frame = CGRect(x: self.view.bounds.size.width, y: self.view.bounds.height, width: 75, height: 75)
tool.image = #imageLiteral(resourceName: "pen")
self.view.addSubview(tool)
}
#IBAction func eraser(_ sender: AnyObject) {
if (isDrawing) {
(red,green,blue) = (1,1,1)
tool.image = #imageLiteral(resourceName: "eraser")
toolicon.setImage(#imageLiteral(resourceName: "pen"), for: .normal)
(lw) = (50)
} else {
(red,green,blue) = (0,0,0)
tool.image = #imageLiteral(resourceName: "pen")
toolicon.setImage(#imageLiteral(resourceName: "eraser"), for: .normal)
(lw) = (2.5)
}
isDrawing = !isDrawing
}
func delay(_ delay:Double, closure:#escaping ()->()) {
let when = DispatchTime.now() + delay
DispatchQueue.main.asyncAfter(deadline: when, execute: closure)
}
#IBAction func save(_ sender: AnyObject) {
if let image = imageView.image {
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
self.imageView.image = nil
// the alert view
let alert = UIAlertController(title: "", message: "Thank you, your guestbook entry has been saved. Redirecting you the home page", preferredStyle: .alert)
self.present(alert, animated: true, completion: nil)
// change to desired number of seconds (in this case 5 seconds)
let when = DispatchTime.now() + 2.5
DispatchQueue.main.asyncAfter(deadline: when){
// your code with delay
alert.dismiss(animated: true, completion: nil)
}
delay(3.0) {
// do stuff
self.performSegue(withIdentifier: "savetocam", sender: nil)
}
}
}
#IBAction func lineSize(_ sender: AnyObject) {
if sender.tag == 8 {
(lw) = (1)
} else if sender.tag == 9 {
(lw) = (2.5)
} else if sender.tag == 10 {
(lw) = (5)
}
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
swiped = false
if let touch = touches.first {
lastPoint = touch.location(in: self.view)
}
}
#IBAction func colorsPicked(_ sender: AnyObject) {
if sender.tag == 0 {
(red,green,blue) = (0,0,0)
} else if sender.tag == 1 {
(red,green,blue) = (0.25,0.00,0.39)
} else if sender.tag == 2 {
(red,green,blue) = (0.65,0.62,0.75)
} else if sender.tag == 3 {
(red,green,blue) = (1.00,0.00,0.00)
} else if sender.tag == 4 {
(red,green,blue) = (0.49,0.77,0.46)
} else if sender.tag == 5 {
(red,green,blue) = (0.0,0.68,0.94)
} else if sender.tag == 6 {
(red,green,blue) = (0.96,0.56,0.34)
} else if sender.tag == 7 {
(red,green,blue) = (1.00,0.95,0.00)
}
}
#IBAction func reset(_ sender: AnyObject) {
self.imageView.image = nil
}
func drawLines(fromPoint:CGPoint,toPoint:CGPoint) {
UIGraphicsBeginImageContext(self.view.frame.size)
imageView.image?.draw(in: CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
let context = UIGraphicsGetCurrentContext()
context?.move(to:CGPoint(x: fromPoint.x, y: fromPoint.y))
context?.addLine(to: CGPoint(x: toPoint.x, y: toPoint.y))
context?.setBlendMode(CGBlendMode.normal)
context?.setLineCap(CGLineCap.round)
context?.setLineWidth(lw)
context?.setStrokeColor(UIColor(red: red, green: green, blue: blue, alpha: alpha).cgColor)
context?.strokePath()
imageView.image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
swiped = true
if let touch = touches.first {
let currentPoint = touch.location(in: self.view)
drawLines(fromPoint: lastPoint, toPoint: currentPoint)
lastPoint = currentPoint
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
if !swiped {
drawLines(fromPoint: lastPoint, toPoint: lastPoint)
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}