Strange Issue With Transparent PNG Files From iOS Photo Library

There doesn't seem to be anything wrong with your code, so I have to wonder if your images really, truly have transparency?

Here's a simple example to check. It looks like this when run:

The code creates Red and Blue image views, with .contentMode = .center.

Tapping the "Create" button will generate a UIImage using SF Symbol -- green with transparent background, the size of the Red image view -- and save it to Photos in PNG format with transparency.

Tapping the "Load" button will bring up the image picker. Selecting an image (such as the one just created and saved) will load the image and - using your extension - resize it to 80 x 80 and assign it to the .image property of the Blue image view.

As you can see, the image loaded from the Photo Picker still has its transparency.

Your UIImage extension for resizing

extension UIImage {
    func resizeThisImage(toNewWidth inNewWidth: CGFloat? = nil, toNewHeight inNewHeight: CGFloat? = nil) -> UIImage? {
        guard nil == inNewWidth,
              nil == inNewHeight else {
            var scaleX: CGFloat = (inNewWidth ?? size.width) / size.width
            var scaleY: CGFloat = (inNewHeight ?? size.height) / size.height
            
            scaleX = nil == inNewWidth ? scaleY : scaleX
            scaleY = nil == inNewHeight ? scaleX : scaleY
            
            let destinationSize = CGSize(width: size.width * scaleX, height: size.height * scaleY)
            let destinationRect = CGRect(origin: .zero, size: destinationSize)
            
            UIGraphicsBeginImageContextWithOptions(destinationSize, false, 0)
            defer { UIGraphicsEndImageContext() }   // This makes sure that we get rid of the offscreen context.
            draw(in: destinationRect, blendMode: .normal, alpha: 1)
            return UIGraphicsGetImageFromCurrentImageContext()
        }
        
        return nil
    }
}

UIImage extension to save to Photos in PNG format with transparency

extension UIImage {
    // save to Photos in PNG format with transparency
    func saveToPhotos(completion: @escaping (_ success:Bool) -> ()) {
        if let pngData = self.pngData() {
            PHPhotoLibrary.shared().performChanges({ () -> Void in
                let creationRequest = PHAssetCreationRequest.forAsset()
                let options = PHAssetResourceCreationOptions()
                creationRequest.addResource(with: PHAssetResourceType.photo, data: pngData, options: options)
            }, completionHandler: { (success, error) -> Void in
                if success == false {
                    if let errorString = error?.localizedDescription  {
                        print("Photo could not be saved: \(errorString))")
                    }
                    completion(false)
                } else {
                    print("Photo saved!")
                    completion(true)
                }
            })
        } else {
            completion(false)
        }
    }
}

Example view controller uses (essentially) your func imagePickerController for loading a photo

class TestImageViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    
    var imgViewA: UIImageView = UIImageView()
    var imgViewB: UIImageView = UIImageView()

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let vStack = UIStackView()
        vStack.axis = .vertical
        vStack.spacing = 20
        
        let btnStack = UIStackView()
        btnStack.axis = .horizontal
        btnStack.distribution = .fillEqually
        btnStack.spacing = 20
        
        let btnCreate = UIButton()
        let btnLoad = UIButton()

        btnCreate.setTitle("Create", for: [])
        btnLoad.setTitle("Load", for: [])
        
        [btnCreate, btnLoad].forEach { b in
            b.setTitleColor(.white, for: .normal)
            b.setTitleColor(.lightGray, for: .highlighted)
            b.backgroundColor = UIColor(red: 0.0, green: 0.5, blue: 0.75, alpha: 1.0)
            btnStack.addArrangedSubview(b)
        }
        
        vStack.translatesAutoresizingMaskIntoConstraints = false
        
        view.addSubview(vStack)
        
        [btnStack, imgViewA, imgViewB].forEach { v in
            vStack.addArrangedSubview(v)
        }
        
        [imgViewA, imgViewB].forEach { v in
            v.contentMode = .center
        }
        
        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            vStack.centerXAnchor.constraint(equalTo: g.centerXAnchor),
            vStack.centerYAnchor.constraint(equalTo: g.centerYAnchor),
            vStack.widthAnchor.constraint(equalToConstant: 200.0),
            
            imgViewA.heightAnchor.constraint(equalTo: imgViewA.widthAnchor),
            imgViewB.heightAnchor.constraint(equalTo: imgViewB.widthAnchor),
        ])
        
        imgViewA.backgroundColor = .red
        imgViewB.backgroundColor = .blue
        
        btnCreate.addTarget(self, action: #selector(self.createAndSave(_:)), for: .touchUpInside)
        btnLoad.addTarget(self, action: #selector(importPicture(_:)), for: .touchUpInside)
        
    }
    
    @objc func createAndSave(_ sender: Any) {
        
        let w = imgViewA.frame.width
        
        // create a Green image with transparent background
        if let img = drawSystemImage("a.circle.fill", at: 80, centeredIn: CGSize(width: w, height: w)) {
            imgViewA.image = img
            
            // save it to Photos in PNG format with transparency
            img.saveToPhotos { (success) in
                if success {
                    // image saved to photos
                    print("saved")
                }
                else {
                    // image not saved
                    fatalError("save failed")
                }
            }
        }
        
    }
    
    // create UIImage from SF Symbol system image
    //  at Point Size
    //  centered in CGSize
    // will draw symbol in Green on transparent background
    private func drawSystemImage(_ sysName: String, at pointSize: CGFloat, centeredIn size: CGSize) -> UIImage? {
        let cfg = UIImage.SymbolConfiguration(pointSize: pointSize)
        guard let img = UIImage(systemName: sysName, withConfiguration: cfg)?.withTintColor(.green, renderingMode: .alwaysOriginal) else { return nil }
        let x = (size.width - img.size.width) * 0.5
        let y = (size.height - img.size.height) * 0.5
        let renderer = UIGraphicsImageRenderer(size: size)
        return renderer.image { context in
            img.draw(in: CGRect(origin: CGPoint(x: x, y: y), size: img.size))
        }
    }
    
    @objc func importPicture(_ sender: Any) {
        let picker = UIImagePickerController()
        picker.allowsEditing = true
        picker.delegate = self
        present(picker, animated: true)
    }
    
    func imagePickerController(_ inPicker: UIImagePickerController, didFinishPickingMediaWithInfo inInfo: [UIImagePickerController.InfoKey: Any]) {
        let info = Dictionary(uniqueKeysWithValues: inInfo.map { key, value in (key.rawValue, value) })
        
        guard let image = (info[UIImagePickerController.InfoKey.editedImage.rawValue] as? UIImage ?? info[UIImagePickerController.InfoKey.originalImage.rawValue] as? UIImage)?.resizeThisImage(toNewWidth: 80) else { return }
        
        // organization?.icon = image
        
        inPicker.dismiss(animated: true) {
            DispatchQueue.main.async { [weak self] in
                self?.imgViewB.image = image
                //self?.imageButton?.image = image
                //self?.imageButton?.alpha = 1.0
                //self?.imageButton?.tintColor = self?.view.tintColor
                //self?.updateUI()
            }
        }
    }
}