QRCodeImage for iOS and OSX: allows to create a correct QR code without blur (ported from https://gist.github.com/snej/c210cc4cbfe8fd277186)

QRImage.swift

//
//  QRImage.swift
//  QRCodeSample
//
//  Created by ing.conti on 08/06/2019.
//  Copyright © 2019 ing.conti. All rights reserved.
//



#if os(iOS)
import UIKit
typealias QRImage = UIImage
#elseif os(OSX)
import Cocoa
typealias QRImage = NSImage
#endif

func QRCodeImageWith(string: String, size: CGFloat = 500) -> QRImage?{

    guard let data = string.data(using: .utf8) else {
        return nil
    }
    
    return QRCodeImageWith(data: data, size: size)
}

func QRCodeImageWith(data: Data, size: CGFloat = 500) -> QRImage?{
    
    guard let filter = CIFilter(name: "CIQRCodeGenerator") else {
        return nil
    }
    
    filter.setValue(data, forKey: "inputMessage")
    guard let ciImage = filter.outputImage else {
        return nil
    }
    
    let destRect = CGRect(x: 0, y: 0, width: size, height: size)
    
    
    #if os(iOS)

    let tinyImage = UIImage(ciImage: ciImage)
    if (size <= tinyImage.size.width){
        return tinyImage
    }
    
    
    // Scale image up:
    UIGraphicsBeginImageContext(CGSize(width: size, height: size))
    if let context = UIGraphicsGetCurrentContext(){
        context.interpolationQuality = .none
        tinyImage.draw(in: destRect)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
    return nil
    
    #elseif os(OSX)
    
    let rep = NSCIImageRep(ciImage: ciImage)
    let tinyImage = NSImage()
    tinyImage.addRepresentation(rep)
    if size <= rep.size.width {
        return tinyImage as QRImage
    }
    
    // Scale image up:
    let nsImage = NSImage(size: NSSize(width: size, height: size))
    nsImage.lockFocus()
    
    let ctx = NSGraphicsContext.current
    ctx?.imageInterpolation = NSImageInterpolation.none
    tinyImage.draw(in: destRect)
    nsImage.unlockFocus()
    return nsImage
    

    #endif
}


// SEE below for usage on iOS and OSX

ViewController

//
//  ViewController.swift
//  QRCodeSample
//
//  Created by ing.conti on 25/05/2019.
//  Copyright © 2019 ing.conti. All rights reserved.
//

import Cocoa
import CoreImage



class ViewController: NSViewController {
    
    private var qrcodeImage: CIImage?
    
    @IBOutlet weak var QRCodeImageView: NSImageView!
    @IBOutlet weak var txt: NSTextField!
    

    @IBAction func generate(_ sender: Any) {

        if txt.stringValue == "" {
            txt.stringValue = "hello"
        }
        
        QRCodeImageView.wantsLayer = true
        
        guard let data = txt.stringValue.data(using: String.Encoding.isoLatin1, allowLossyConversion: false) else {
            return
        }
        
        let tempSwift = QRCodeImageWith(data: data, size: 300)
        QRCodeImageView.image = tempSwift
        
        return
        
    }
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        generate(self)
    }
    
    override var representedObject: Any? {
        didSet {
            // Update the view, if already loaded.
        }
    }
    
    
}

ViewController.swift

//
//  ViewController.swift
//  QRCodeSampleiOS
//
//  Created by ing.conti on 08/06/2019.
//  Copyright © 2019 ing.conti. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var txt: UITextField!
    @IBOutlet weak var QRCodeImageView: UIImageView!
    
    override func viewDidLoad() {
        super.viewDidLoad()

        if txt.text == "" {
            txt.text = "hello"
        }

        generate(UIButton())
    }

    @IBAction func generate(_ sender: UIButton) {
        
        
        guard let data = txt.text?.data(using: String.Encoding.isoLatin1, allowLossyConversion: false) else {
            return
        }
        
        let tempSwift = QRCodeImageWith(data: data, size: 300)
        QRCodeImageView.image = tempSwift
        
        return
        
    }
    
    
}