QRCode generation test

// QRCode generation test

import UIKit

class TestViewController: UIViewController {

    let imgView: UIImageView = {
        let v = UIImageView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .green
        return v
    }()
    let btn: UIButton = {
        let v = UIButton(type: .system)
        v.translatesAutoresizingMaskIntoConstraints = false
        v.setTitle("Run Test", for: [])
        v.backgroundColor = .yellow
        return v
    }()

    var tm1: CFAbsoluteTime!
    var tm2: CFAbsoluteTime!
    var tm3: CFAbsoluteTime!
    var tm4: CFAbsoluteTime!

    let strs: [String] = [
        "Simple Text",
        "Longer string here.",
        "This is a much longer string for generating a QR Code image!",
    ]

    var idx: Int = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(btn)
        view.addSubview(imgView)

        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            btn.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
            btn.centerXAnchor.constraint(equalTo: g.centerXAnchor),

            imgView.topAnchor.constraint(equalTo: btn.bottomAnchor, constant: 20.0),
            imgView.centerXAnchor.constraint(equalTo: g.centerXAnchor),

            imgView.widthAnchor.constraint(equalToConstant: 240.0),
            imgView.heightAnchor.constraint(equalTo: imgView.widthAnchor),
        ])

        btn.addTarget(self, action: #selector(self.didTap(_:)), for: .touchUpInside)

    }

    @objc func didTap(_ sender: Any) {

        let str = strs[idx % strs.count]

        tm1 = CFAbsoluteTimeGetCurrent()

        imgView.generateQRCode(from: str) { image in
            self.tm2 = CFAbsoluteTimeGetCurrent()
            DispatchQueue.main.async {
                self.tm3 = CFAbsoluteTimeGetCurrent()
                self.imgView.image = image;
                self.tm4 = CFAbsoluteTimeGetCurrent()
                self.showResults(str)
            }
        }

    }

    func showResults(_ s: String) -> Void {

        let elapsed1 = tm2 - tm1
        let elapsed2 = tm3 - tm2
        let elapsed3 = tm4 - tm3
        let elapsed4 = tm4 - tm1

        let nf = NumberFormatter()
        nf.maximumFractionDigits = 6

        idx += 1

        print("Generate from string:", s)
        print("elapsed time to generate image:", nf.string(from: NSNumber(value: elapsed1))!)
        print("elapsed time from generate to async execution:", nf.string(from: NSNumber(value: elapsed2))!)
        print("elapsed time to set imageView.image:", nf.string(from: NSNumber(value: elapsed3))!)
        print("overall elapsed time:", nf.string(from: NSNumber(value: elapsed4))!)
        print()

    }

}

// Console output - each test button is tapped 4 times
// on first tap, execution takes much longer than subsequent taps

------------------

iPhone 7 - Device / 13.3

Generate from string: Simple Text
elapsed time to generate image: 0.157093
elapsed time from generate to async execution: 0.000097
elapsed time to set imageView.image: 0.100747
overall elapsed time: 0.257937

Generate from string: Longer string here.
elapsed time to generate image: 0.002767
elapsed time from generate to async execution: 0.000066
elapsed time to set imageView.image: 0.003793
overall elapsed time: 0.006626

Generate from string: This is a much longer string for generating a QR Code image!
elapsed time to generate image: 0.002132
elapsed time from generate to async execution: 0.000047
elapsed time to set imageView.image: 0.003155
overall elapsed time: 0.005334

Generate from string: Simple Text
elapsed time to generate image: 0.005457
elapsed time from generate to async execution: 0.000163
elapsed time to set imageView.image: 0.004744
overall elapsed time: 0.010364

------------------

iPad Air - Device / 12.1 / 1st gen from 2013

Generate from string: Simple Text
elapsed time to generate image: .509212
elapsed time from generate to async execution: .000279
elapsed time to set imageView.image: .321866
overall elapsed time: .831357

Generate from string: Longer string here.
elapsed time to generate image: .00809
elapsed time from generate to async execution: .000144
elapsed time to set imageView.image: .009812
overall elapsed time: .018046

Generate from string: This is a much longer string for generating a QR Code image!
elapsed time to generate image: .008096
elapsed time from generate to async execution: .000157
elapsed time to set imageView.image: .01149
overall elapsed time: .019743

Generate from string: Simple Text
elapsed time to generate image: .010136
elapsed time from generate to async execution: .000077
elapsed time to set imageView.image: .005702
overall elapsed time: .015915

------------------

iPhone 8 / Simulator / 14.0

Generate from string: Simple Text
elapsed time to generate image: 0.133525
elapsed time from generate to async execution: 0.000032
elapsed time to set imageView.image: 0.148432
overall elapsed time: 0.281989

Generate from string: Longer string here.
elapsed time to generate image: 0.001354
elapsed time from generate to async execution: 0.000053
elapsed time to set imageView.image: 0.052862
overall elapsed time: 0.054269

Generate from string: This is a much longer string for generating a QR Code image!
elapsed time to generate image: 0.002095
elapsed time from generate to async execution: 0.000026
elapsed time to set imageView.image: 0.052522
overall elapsed time: 0.054643

Generate from string: Simple Text
elapsed time to generate image: 0.001223
elapsed time from generate to async execution: 0.00005
elapsed time to set imageView.image: 0.052479
overall elapsed time: 0.053752