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axiom-photo-library-ref

@CharlesWiltgen/Axiom
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Reference — PHPickerViewController, PHPickerConfiguration, PhotosPicker, PhotosPickerItem, Transferable, PHPhotoLibrary, PHAsset, PHAssetCreationRequest, PHFetchResult, PHAuthorizationStatus, limited library APIs

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SKILL.md

name axiom-photo-library-ref
description Reference — PHPickerViewController, PHPickerConfiguration, PhotosPicker, PhotosPickerItem, Transferable, PHPhotoLibrary, PHAsset, PHAssetCreationRequest, PHFetchResult, PHAuthorizationStatus, limited library APIs
skill_type reference
version 1.0.0

Photo Library API Reference

Quick Reference

// SWIFTUI PHOTO PICKER (iOS 16+)
import PhotosUI

@State private var item: PhotosPickerItem?

PhotosPicker(selection: $item, matching: .images) {
    Text("Select Photo")
}
.onChange(of: item) { _, newItem in
    Task {
        if let data = try? await newItem?.loadTransferable(type: Data.self) {
            // Use image data
        }
    }
}

// UIKIT PHOTO PICKER (iOS 14+)
var config = PHPickerConfiguration()
config.selectionLimit = 1
config.filter = .images
let picker = PHPickerViewController(configuration: config)
picker.delegate = self

// SAVE TO CAMERA ROLL
try await PHPhotoLibrary.shared().performChanges {
    PHAssetCreationRequest.creationRequestForAsset(from: image)
}

// CHECK PERMISSION
let status = PHPhotoLibrary.authorizationStatus(for: .readWrite)

PHPickerViewController (iOS 14+)

System photo picker for UIKit apps. No permission required.

Configuration

import PhotosUI

var config = PHPickerConfiguration()

// Selection limit (0 = unlimited)
config.selectionLimit = 5

// Filter by asset type
config.filter = .images

// Use photo library (enables asset identifiers)
config = PHPickerConfiguration(photoLibrary: .shared())

// Preferred asset representation
config.preferredAssetRepresentationMode = .automatic  // default
// .current - original format
// .compatible - converted to compatible format

Filter Options

// Basic filters
PHPickerFilter.images
PHPickerFilter.videos
PHPickerFilter.livePhotos

// Combined filters
PHPickerFilter.any(of: [.images, .videos])

// Exclusion filters (iOS 15+)
PHPickerFilter.all(of: [.images, .not(.screenshots)])
PHPickerFilter.not(.livePhotos)

// Playback style filters (iOS 17+)
PHPickerFilter.any(of: [.cinematicVideos, .slomoVideos])

Presenting

let picker = PHPickerViewController(configuration: config)
picker.delegate = self
present(picker, animated: true)

Delegate

extension ViewController: PHPickerViewControllerDelegate {

    func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]) {
        picker.dismiss(animated: true)

        for result in results {
            // Get asset identifier (if using PHPickerConfiguration(photoLibrary:))
            let identifier = result.assetIdentifier

            // Load as UIImage
            result.itemProvider.loadObject(ofClass: UIImage.self) { object, error in
                guard let image = object as? UIImage else { return }
                DispatchQueue.main.async {
                    self.displayImage(image)
                }
            }

            // Load as Data
            result.itemProvider.loadDataRepresentation(forTypeIdentifier: UTType.image.identifier) { data, error in
                guard let data else { return }
                // Use data
            }

            // Load Live Photo
            result.itemProvider.loadObject(ofClass: PHLivePhoto.self) { object, error in
                guard let livePhoto = object as? PHLivePhoto else { return }
                // Use live photo
            }
        }
    }
}

PHPickerResult Properties

Property Type Description
itemProvider NSItemProvider Provides selected asset data
assetIdentifier String? PHAsset identifier (if using photoLibrary config)

PhotosPicker (SwiftUI, iOS 16+)

SwiftUI view for photo selection. No permission required.

Basic Usage

import SwiftUI
import PhotosUI

// Single selection
@State private var selectedItem: PhotosPickerItem?

PhotosPicker(selection: $selectedItem, matching: .images) {
    Label("Select Photo", systemImage: "photo")
}

// Multiple selection
@State private var selectedItems: [PhotosPickerItem] = []

PhotosPicker(
    selection: $selectedItems,
    maxSelectionCount: 5,
    matching: .images
) {
    Text("Select Photos")
}

Filters

// Images only
matching: .images

// Videos only
matching: .videos

// Images and videos
matching: .any(of: [.images, .videos])

// Live Photos
matching: .livePhotos

// Exclude screenshots (iOS 15+)
matching: .all(of: [.images, .not(.screenshots)])

Selection Behavior

PhotosPicker(
    selection: $items,
    maxSelectionCount: 10,
    selectionBehavior: .ordered,  // .default, .ordered, .continuous
    matching: .images
) { ... }
Behavior Description
.default Standard multi-select
.ordered Selection order preserved
.continuous Live updates as user selects (iOS 17+)

Embedded Picker (iOS 17+)

PhotosPicker(
    selection: $items,
    maxSelectionCount: 10,
    selectionBehavior: .continuous,
    matching: .images
) {
    Text("Select")
}
.photosPickerStyle(.inline)  // Embed in view hierarchy
.photosPickerDisabledCapabilities([.selectionActions])
.photosPickerAccessoryVisibility(.hidden, edges: .all)
Style Description
.presentation Modal sheet (default)
.inline Embedded in view
.compact Single row
Disabled Capability Effect
.search Hide search bar
.collectionNavigation Hide albums
.stagingArea Hide selection review
.selectionActions Hide Add/Cancel
Accessory Visibility Description
.hidden, .automatic, .visible Per edge

HDR Preservation (iOS 17+)

PhotosPicker(
    selection: $items,
    matching: .images,
    preferredItemEncoding: .current  // Don't transcode, preserve HDR
) { ... }
Encoding Description
.automatic System decides format
.current Original format, preserves HDR
.compatible Force compatible format

Loading Images from PhotosPickerItem

// Load as Data (most reliable)
if let data = try? await item.loadTransferable(type: Data.self),
   let image = UIImage(data: data) {
    // Use image
}

// Custom Transferable for direct UIImage
struct ImageTransferable: Transferable {
    let image: UIImage

    static var transferRepresentation: some TransferRepresentation {
        DataRepresentation(importedContentType: .image) { data in
            guard let image = UIImage(data: data) else {
                throw TransferError.importFailed
            }
            return ImageTransferable(image: image)
        }
    }
}

// Usage
if let result = try? await item.loadTransferable(type: ImageTransferable.self) {
    let image = result.image
}

PhotosPickerItem Properties

Property Type Description
itemIdentifier String Unique identifier
supportedContentTypes [UTType] Available representations

PhotosPickerItem Methods

// Load transferable
func loadTransferable<T: Transferable>(type: T.Type) async throws -> T?

// Load with progress
func loadTransferable<T: Transferable>(
    type: T.Type,
    completionHandler: @escaping (Result<T?, Error>) -> Void
) -> Progress

PHPhotoLibrary

Access and modify the photo library.

Authorization Status

// Check current status
let status = PHPhotoLibrary.authorizationStatus(for: .readWrite)

// Request authorization
let newStatus = await PHPhotoLibrary.requestAuthorization(for: .readWrite)

PHAuthorizationStatus

Status Description
.notDetermined User hasn't been asked
.restricted Parental controls limit access
.denied User denied access
.authorized Full access granted
.limited Access to user-selected photos only (iOS 14+)

Access Levels

// Read and write
PHPhotoLibrary.requestAuthorization(for: .readWrite)

// Add only (save photos, no reading)
PHPhotoLibrary.requestAuthorization(for: .addOnly)

Limited Library Picker

// Present picker to expand limited selection
@MainActor
func presentLimitedLibraryPicker() {
    guard let viewController = UIApplication.shared.keyWindow?.rootViewController else { return }
    PHPhotoLibrary.shared().presentLimitedLibraryPicker(from: viewController)
}

// With completion handler
PHPhotoLibrary.shared().presentLimitedLibraryPicker(from: viewController) { identifiers in
    // identifiers: asset IDs user added
}

Performing Changes

// Async changes
try await PHPhotoLibrary.shared().performChanges {
    // Create, update, or delete assets
}

// With completion handler
PHPhotoLibrary.shared().performChanges({
    // Changes
}) { success, error in
    // Handle result
}

Change Observer

class PhotoObserver: NSObject, PHPhotoLibraryChangeObserver {

    override init() {
        super.init()
        PHPhotoLibrary.shared().register(self)
    }

    deinit {
        PHPhotoLibrary.shared().unregisterChangeObserver(self)
    }

    func photoLibraryDidChange(_ changeInstance: PHChange) {
        // Handle changes
        guard let changes = changeInstance.changeDetails(for: fetchResult) else { return }

        DispatchQueue.main.async {
            // Update UI with new fetch result
            let newResult = changes.fetchResultAfterChanges
        }
    }
}

PHAsset

Represents an asset in the photo library.

Fetching Assets

// All photos
let allPhotos = PHAsset.fetchAssets(with: .image, options: nil)

// With options
let options = PHFetchOptions()
options.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
options.fetchLimit = 100
options.predicate = NSPredicate(format: "mediaType == %d", PHAssetMediaType.image.rawValue)

let recentPhotos = PHAsset.fetchAssets(with: options)

// By identifier
let assets = PHAsset.fetchAssets(withLocalIdentifiers: [identifier], options: nil)

Asset Properties

Property Type Description
localIdentifier String Unique ID
mediaType PHAssetMediaType .image, .video, .audio
mediaSubtypes PHAssetMediaSubtype .photoLive, .photoPanorama, etc.
pixelWidth Int Width in pixels
pixelHeight Int Height in pixels
creationDate Date? When taken
modificationDate Date? Last modified
location CLLocation? GPS location
duration TimeInterval Video duration
isFavorite Bool Marked as favorite
isHidden Bool In hidden album

PHAssetMediaType

Type Value
.unknown 0
.image 1
.video 2
.audio 3

PHAssetMediaSubtype

Subtype Description
.photoPanorama Panoramic photo
.photoHDR HDR photo
.photoScreenshot Screenshot
.photoLive Live Photo
.photoDepthEffect Portrait mode
.videoStreamed Streamed video
.videoHighFrameRate Slo-mo video
.videoTimelapse Timelapse
.videoCinematic Cinematic mode

PHAssetCreationRequest

Create new assets in the photo library.

Creating from UIImage

try await PHPhotoLibrary.shared().performChanges {
    PHAssetCreationRequest.creationRequestForAsset(from: image)
}

Creating from File URL

try await PHPhotoLibrary.shared().performChanges {
    PHAssetCreationRequest.creationRequestForAssetFromImage(atFileURL: imageURL)
}

// For video
try await PHPhotoLibrary.shared().performChanges {
    PHAssetCreationRequest.creationRequestForAssetFromVideo(atFileURL: videoURL)
}

Creating with Resources

try await PHPhotoLibrary.shared().performChanges {
    let request = PHAssetCreationRequest.forAsset()

    // Add photo resource
    let options = PHAssetResourceCreationOptions()
    options.shouldMoveFile = true  // Move instead of copy

    request.addResource(with: .photo, fileURL: photoURL, options: options)

    // Set creation date
    request.creationDate = Date()

    // Set location
    request.location = CLLocation(latitude: 37.7749, longitude: -122.4194)
}

Deferred Photo Proxy (iOS 17+)

Save camera proxy photos for background processing:

// From AVCaptureDeferredPhotoProxy callback
try await PHPhotoLibrary.shared().performChanges {
    let request = PHAssetCreationRequest.forAsset()

    // Use .photoProxy to trigger deferred processing
    request.addResource(with: .photoProxy, data: proxyData, options: nil)
}
Resource Type Description
.photo Standard photo
.video Video file
.photoProxy Deferred processing proxy (iOS 17+)
.adjustmentData Edit adjustments

Getting Created Asset

try await PHPhotoLibrary.shared().performChanges {
    let request = PHAssetCreationRequest.forAsset()
    request.addResource(with: .photo, fileURL: url, options: nil)

    // Get placeholder for later fetching
    let placeholder = request.placeholderForCreatedAsset
    // placeholder.localIdentifier available after changes complete
}

PHFetchResult

Ordered list of assets from a fetch.

Properties

Property Type Description
count Int Number of items
firstObject T? First item
lastObject T? Last item

Methods

// Access by index
let asset = fetchResult.object(at: 0)
let asset = fetchResult[0]

// Get multiple
let assets = fetchResult.objects(at: IndexSet(0..<10))

// Iteration
fetchResult.enumerateObjects { asset, index, stop in
    // Process asset
    if shouldStop {
        stop.pointee = true
    }
}

// Check contains
let contains = fetchResult.contains(asset)
let index = fetchResult.index(of: asset)

PHImageManager

Request images from assets.

Request Image

let manager = PHImageManager.default()

let options = PHImageRequestOptions()
options.deliveryMode = .highQualityFormat
options.resizeMode = .exact
options.isNetworkAccessAllowed = true  // For iCloud photos

let targetSize = CGSize(width: 300, height: 300)

manager.requestImage(
    for: asset,
    targetSize: targetSize,
    contentMode: .aspectFill,
    options: options
) { image, info in
    guard let image else { return }

    // Check if this is the final image
    let isDegraded = (info?[PHImageResultIsDegradedKey] as? Bool) ?? false
    if !isDegraded {
        // Final high-quality image
    }
}

PHImageRequestOptions

Property Type Description
deliveryMode PHImageRequestOptionsDeliveryMode Quality preference
resizeMode PHImageRequestOptionsResizeMode Resize behavior
isNetworkAccessAllowed Bool Allow iCloud download
isSynchronous Bool Synchronous request
progressHandler Block Download progress
allowSecondaryDegradedImage Bool Extra callback during deferred processing (iOS 17+)

Secondary Degraded Image (iOS 17+)

For photos undergoing deferred processing, get an intermediate quality image:

let options = PHImageRequestOptions()
options.allowSecondaryDegradedImage = true

// Callback order:
// 1. Low quality (immediate, isDegraded = true)
// 2. Medium quality (new, isDegraded = true) -- while processing
// 3. Final quality (isDegraded = false)

Delivery Modes

Mode Description
.opportunistic Fast thumbnail, then high quality
.highQualityFormat Only high quality
.fastFormat Only fast/degraded

Request Video

manager.requestAVAsset(forVideo: asset, options: nil) { avAsset, audioMix, info in
    guard let avAsset else { return }
    // Use AVAsset for playback
}

// Or export to file
manager.requestExportSession(
    forVideo: asset,
    options: nil,
    exportPreset: AVAssetExportPresetHighestQuality
) { session, info in
    session?.outputURL = outputURL
    session?.outputFileType = .mp4
    session?.exportAsynchronously { ... }
}

PHChange

Represents changes to the photo library.

Getting Change Details

func photoLibraryDidChange(_ changeInstance: PHChange) {
    guard let changes = changeInstance.changeDetails(for: fetchResult) else { return }

    // Check what changed
    let hasIncrementalChanges = changes.hasIncrementalChanges
    let insertedIndexes = changes.insertedIndexes
    let removedIndexes = changes.removedIndexes
    let changedIndexes = changes.changedIndexes

    // Get new fetch result
    let newResult = changes.fetchResultAfterChanges

    // Update collection view
    DispatchQueue.main.async {
        if hasIncrementalChanges {
            collectionView.performBatchUpdates {
                if let removed = removedIndexes {
                    collectionView.deleteItems(at: removed.map { IndexPath(item: $0, section: 0) })
                }
                if let inserted = insertedIndexes {
                    collectionView.insertItems(at: inserted.map { IndexPath(item: $0, section: 0) })
                }
                if let changed = changedIndexes {
                    collectionView.reloadItems(at: changed.map { IndexPath(item: $0, section: 0) })
                }
            }
        } else {
            collectionView.reloadData()
        }
    }
}

Common Code Patterns

Complete Photo Gallery View

import SwiftUI
import Photos

@MainActor
class PhotoGalleryViewModel: ObservableObject {
    @Published var assets: [PHAsset] = []
    @Published var authorizationStatus: PHAuthorizationStatus = .notDetermined

    func requestAccess() async {
        authorizationStatus = await PHPhotoLibrary.requestAuthorization(for: .readWrite)

        if authorizationStatus == .authorized || authorizationStatus == .limited {
            fetchAssets()
        }
    }

    func fetchAssets() {
        let options = PHFetchOptions()
        options.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        options.fetchLimit = 100

        let result = PHAsset.fetchAssets(with: .image, options: options)
        assets = result.objects(at: IndexSet(0..<result.count))
    }

    func expandLimitedAccess(from viewController: UIViewController) {
        PHPhotoLibrary.shared().presentLimitedLibraryPicker(from: viewController)
    }
}

struct PhotoGalleryView: View {
    @StateObject private var viewModel = PhotoGalleryViewModel()

    var body: some View {
        Group {
            switch viewModel.authorizationStatus {
            case .authorized, .limited:
                PhotoGridView(assets: viewModel.assets)
            case .denied, .restricted:
                PermissionDeniedView()
            case .notDetermined:
                RequestAccessView {
                    Task { await viewModel.requestAccess() }
                }
            @unknown default:
                EmptyView()
            }
        }
        .task {
            await viewModel.requestAccess()
        }
    }
}

Resources

Docs: /photosui/phpickerviewcontroller, /photosui/photospicker, /photos/phphotolibrary, /photos/phasset, /photos/phimagemanager

Skills: axiom-photo-library, axiom-camera-capture