Why is the image quality so low? (swift)

Question

I didn't like apples image picker so I decided to implement my own. I just finished the stage of getting all the users photos and displaying them in a collection view although I noticed that the difference in image quality is horrible. Here is my code:

import UIKit
import Photos
import PhotosUI
import Foundation

private let reuseIdentifier = "Cell"
var selectedImage = UIImage()

class CollectionVC: UICollectionViewController, UICollectionViewDelegateFlowLayout {

    
    var imageArray = [UIImage]()
    
    override func viewDidLoad() {
        super.viewDidLoad()

     grapPhotos()
       

        
    }


    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        
        return imageArray.count
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath as IndexPath)
        let imageView = cell.viewWithTag(1) as! UIImageView
        
        
        cell.layer.cornerRadius = 4
        imageView.image = imageArray[indexPath.row]
    
        
        return cell
    }
    override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        
        let selectedImageName = imageArray[indexPath.item]
        print(selectedImageName)
        selectedImage = selectedImageName
        performSegue(withIdentifier: "Custom", sender: self)
    }
    
    func grapPhotos() {
        
        let imgManager = PHImageManager.default()
        let requestOptions = PHImageRequestOptions()
        requestOptions.isSynchronous = true
        requestOptions.deliveryMode = .highQualityFormat
        
        
        let fetchOptions = PHFetchOptions()
        fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        fetchOptions.predicate = NSPredicate(format: "mediaType = %d || mediaType = %d", PHAssetMediaType.image.rawValue, PHAssetMediaType.video.rawValue)
        
        if let fetchResult : PHFetchResult = PHAsset.fetchAssets(with: fetchOptions) {
            
            if fetchResult.count > 0 {
                
                for i in 0..<fetchResult.count {
                    imgManager.requestImage(for: fetchResult.object(at: i), targetSize: CGSize(width: 200, height: 200), contentMode: .aspectFill, options: requestOptions, resultHandler: {
                        
                        image, error in
                        
                        
                        self.imageArray.append(image!)
                        
                        
                    })
        
                    
                }
            }
            else {
                self.collectionView?.reloadData()
                print("No Photos")
            }
        }
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        
        let width = collectionView.frame.width / 3 - 6
        
        
        
        return CGSize(width: width, height: width)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        
        return 6.0
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        
        return 6.0
    }
}

I don't really know much about working with images so if anyone could help me out on displaying higher quality images that would be great.

Answer 1

This really works))

for index in 0..<fetchResult.count {
        let asset = fetchResult.object(at: index) as PHAsset
        let sizeFactor = UIScreen.main.scale
        let deviceSize = UIScreen.main.nativeBounds.size
        manager.requestImage(for: asset,
                                targetSize: CGSize(width: deviceSize.width * sizeFactor,
                                                   height: deviceSize.height * sizeFactor),
                                contentMode: .aspectFit,
                                options: requestOptions,
                                resultHandler: { (uiimage, info) in
            if let image = uiimage {
                allImages.append(image)
            }
        })
    }

You only need to know ->

let sizeFactor = UIScreen.main.scale
let deviceSize = UIScreen.main.nativeBounds.size

Answer 2

Image quality depends on the phone your viewing on - retina screens require more pixels. You'll need to multiply your targetSize by UIScreen.main.scale.

Try setting targetSize: CGSize(width: 200 * UIScreen.main.scale, height: 200.0 * UIScreen.main.scale) in your imgManager.requestImage function.

For Retina displays, the scale factor may be 3.0 or 2.0 and one point can represented by nine or four pixels, respectively. For standard-resolution displays, the scale factor is 1.0 and one point equals one pixel.