FullScreenImageViewController.swift (no zooming) - From "Transition images to full screen animated" @ medium.com

FullScreenImageViewController.swift

//
//  FullScreenImageViewController.swift
//

import UIKit
import TinyConstraints

class FullScreenImageViewController: UIViewController {
    private let octocatImageView: UIImageView = {
        let imageView = UIImageView()
        imageView.contentMode = .scaleAspectFit
        imageView.setHugging(.defaultHigh, for: .horizontal)
        imageView.setCompressionResistance(.defaultHigh, for: .horizontal)
        return imageView
    }()
    
    private lazy var imageViewLandscapeConstraint = octocatImageView.heightToSuperview(isActive: false, usingSafeArea: true)
    private lazy var imageViewPortraitConstraint = octocatImageView.widthToSuperview(isActive: false, usingSafeArea: true)
    
    init(octocat: Octocat, tag: Int) {
        super.init(nibName: nil, bundle: nil)
        octocatImageView.tag = tag
        octocatImageView.image = UIImage(contentsOfFile: octocat.imagePath)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .clear
        
        view.addSubview(octocatImageView)
        
        octocatImageView.centerInSuperview()
        
        // Constraint UIImageView to fit the aspect ratio of the containing image
        let aspectRatio = octocatImageView.intrinsicContentSize.height / octocatImageView.intrinsicContentSize.width
        octocatImageView.heightToWidth(of: octocatImageView, multiplier: aspectRatio)
    }
    
    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)
        traitCollectionChanged(from: previousTraitCollection)
    }
    
    private func traitCollectionChanged(from previousTraitCollection: UITraitCollection?) {
        if traitCollection.horizontalSizeClass != .compact {
            // Ladscape
            imageViewPortraitConstraint.isActive = false
            imageViewLandscapeConstraint.isActive = true
        } else {
            // Portrait
            imageViewLandscapeConstraint.isActive = false
            imageViewPortraitConstraint.isActive = true
        }
    }
}