autolayout - is there a way to automatically resize an image or any content based on the screen size in SWIFT?

Question

I have been trying to find a way to resize an image based on the screen size programmatically without using storyboards?

Answer 1

Go to google (or your favorite search engine) and search for swift add constraints programmatically. This is very, very basic.

Here's a simple example:

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // create image view
        let imgView = UIImageView()
        
        imgView.backgroundColor = .systemYellow
        
        // create image
        let img = UIImage(systemName: "person.fill")
        imgView.image = img
        
        // add imageView to view
        view.addSubview(imgView)
        
        // use auto-layout
        imgView.translatesAutoresizingMaskIntoConstraints = false
        
        // respect safe area
        let g = view.safeAreaLayoutGuide
        
        NSLayoutConstraint.activate([
            // constrain imageView width to view safe-area width
            imgView.leadingAnchor.constraint(equalTo: g.leadingAnchor),
            imgView.trailingAnchor.constraint(equalTo: g.trailingAnchor),
            // aquare image view (1:1 ratio)
            imgView.heightAnchor.constraint(equalTo: imgView.widthAnchor),
            // center vertically
            imgView.centerYAnchor.constraint(equalTo: g.centerYAnchor),
        ])
        
    }
}

Result:

---

Edit - second example... Top third, centered horizontally:

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        navigationController?.setNavigationBarHidden(true, animated: false)
        // create image view
        let imgView = UIImageView()
        
        imgView.backgroundColor = .systemYellow
        
        // create image
        let img = UIImage(systemName: "person.fill")
        imgView.image = img
        
        // add imageView to view
        view.addSubview(imgView)
        
        // use auto-layout
        imgView.translatesAutoresizingMaskIntoConstraints = false
        
        // respect safe area
        let g = view.safeAreaLayoutGuide
        
        NSLayoutConstraint.activate([
            
            // you want the image view at the top?
            imgView.topAnchor.constraint(equalTo: g.topAnchor),
            
            // one-third of the height of the view?
            imgView.heightAnchor.constraint(equalTo: g.heightAnchor, multiplier: 1.0 / 3.0),
            
            // you want a aquare image view (1:1 ratio)?
            imgView.widthAnchor.constraint(equalTo: imgView.heightAnchor),
            
            // you want it centered horizontally?
            imgView.centerXAnchor.constraint(equalTo: g.centerXAnchor),
            
        ])
        
    }
}

On iPhone 8:

On iPhone 12:

On 9.7" iPad Pro, landscape orientation: