UIImage to PHAsset - ios

Question

I am trying to convert UIImage into PHAsset but could not find any solution. All I found is the vice versa (i.e. PHAsset to UIImage).
The scenario is, I am fetching images from a custom directory into PHAssetCollection and showing in UICollectionView. I also want to include few more images here from previous screen which are coming from remote source. I don't want to persist remote images into my directory but want to include them in my UICollectionView.
Kindly suggest me solution or some good alternate so that the source of UICollectionView will be same (i.e. PHAssetCollection)

Answer 1

A bit late to the party, but I'll post my answer for people of the future.
What I did in my app was to take a screenshot and save to a dedicated album in the Photos app.
getAlbum() in the below example is just a helper method that retrieves the photo album.
ImageStoreItem is just a wrapper with two fields: image: UIImage and id: String for the identifier of the original PHAsset.
/**
Saves the image to the album in the Photos app.
- Throws:
- `ImageStore.TypeError.accessDenied`
if the user has denied access to the photo library.
- An error thrown by `PHPhotoLibrary`.
*/
func saveImage(_ image: UIImage) throws {
let album = try getAlbum()
try PHPhotoLibrary.shared().performChangesAndWait {
let imgReq = PHAssetChangeRequest.creationRequestForAsset(from: image),
albReq = PHAssetCollectionChangeRequest(for: album)!
albReq.addAssets([imgReq.placeholderForCreatedAsset] as NSFastEnumeration)
}
}
/**
Fetches images in the app album.
- Throws:
- `ImageStore.TypeError.accessDenied`
if the user has denied access to the photo library.
- An error thrown by `PHPhotoLibrary`.
- `NSError` thrown by `PHImageManager`
if fetching images from the `PHAsset` list failed.
- `Globalerror.unknown` if no image was fetched,
but there is no corresponding error object.
- Returns:
An array of `ImageStoreItem`s with the album items.
*/
func getImages() throws -> [ImageStoreItem] {
let album = try ImageStore.shared.getAlbum(),
assets = PHAsset.fetchAssets(in: album, options: nil)
let size = UIScreen.main.bounds.size,
opt = PHImageRequestOptions()
opt.isSynchronous = true
var res = [ImageStoreItem]()
var err: Error? = nil
let handler: (PHAsset) -> (UIImage?, [AnyHashable : Any]?) -> Void =
{ (asset) in
{ (image, info) in
if let image = image {
let item = ImageStoreItem(image: image,
id: asset.localIdentifier)
res.append(item)
} else if let info = info {
if let error = info[PHImageErrorKey] {
err = error as! NSError
} else {
var userInfo = [String : Any]()
for (key, value) in info {
userInfo[String(describing: key)] = value
}
err = GlobalError.unknown(info: userInfo)
}
}
}
}
assets.enumerateObjects { (asset, _, _) in
PHImageManager.default()
.requestImage(for: asset,
targetSize: size,
contentMode: .default,
options: opt,
resultHandler: handler(asset))
}
if let error = err { throw error }
return res
}
The documentation on the PhotoKit isn't too impressive, but take a look here and there and you'll get the hang of it.

Answer 2

You do not want to convert a PHAsset to UIImage. I do not know if it is possible; it shouldn't be, since PHAsset and UIImage have different properties, behaviours, etc. The vice versa is possible because all the properties of UIImage can be derived from PHAsset but not vice-versa.
Instead, change the data source of the collection view to [UIImage] while converting PHAsset to UIImage instead. This approach is clean and solves your other problem of having to convert UIImage to PHImage.