axiom-photo-library

@CharlesWiltgen/axiom-photo-library

CharlesWiltgen

160

11 forks

Updated 1/6/2026

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PHPicker, PhotosPicker, photo selection, limited library access, presentLimitedLibraryPicker, save to camera roll, PHPhotoLibrary, PHAssetCreationRequest, Transferable, PhotosPickerItem, photo permissions

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$skills install @CharlesWiltgen/axiom-photo-library

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RepositoryCharlesWiltgen/Axiom

Path.claude-plugin/plugins/axiom/skills/axiom-photo-library/SKILL.md

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Scoped Name@CharlesWiltgen/axiom-photo-library

Usage

After installing, this skill will be available to your AI coding assistant.

Verify installation:

skills list

Skill Instructions

name: axiom-photo-library description: PHPicker, PhotosPicker, photo selection, limited library access, presentLimitedLibraryPicker, save to camera roll, PHPhotoLibrary, PHAssetCreationRequest, Transferable, PhotosPickerItem, photo permissions skill_type: discipline version: 1.0.0 last_updated: 2026-01-03 apple_platforms: iOS 14+, iPadOS 14+, macOS 13+

Photo Library Access with PhotoKit

Guides you through photo picking, limited library handling, and saving photos to the camera roll using privacy-forward patterns.

When to Use This Skill

Use when you need to:

☑ Let users select photos from their library
☑ Handle limited photo library access
☑ Save photos/videos to the camera roll
☑ Choose between PHPicker and PhotosPicker
☑ Load images from PhotosPickerItem
☑ Observe photo library changes
☑ Request appropriate permission level

Example Prompts

"How do I let users pick photos in SwiftUI?" "User says they can't see their photos" "How do I save a photo to the camera roll?" "What's the difference between PHPicker and PhotosPicker?" "How do I handle limited photo access?" "User granted limited access but can't see photos" "How do I load an image from PhotosPickerItem?"

Red Flags

Signs you're making this harder than it needs to be:

❌ Using UIImagePickerController (deprecated for photo selection)
❌ Requesting full library access when picker suffices (privacy violation)
❌ Ignoring .limited authorization status (users can't expand selection)
❌ Not handling Transferable loading failures (crashes on large photos)
❌ Synchronously loading images from picker results (blocks UI)
❌ Using PhotoKit APIs when you only need to pick photos (over-engineering)
❌ Assuming .authorized after user grants access (could be .limited)

Mandatory First Steps

Before implementing photo library features:

1. Choose Your Approach

What do you need?

┌─ User picks photos (no library browsing)?
│  ├─ SwiftUI app → PhotosPicker (iOS 16+)
│  └─ UIKit app → PHPickerViewController (iOS 14+)
│  └─ NO library permission needed! Picker handles it.
│
├─ Display user's full photo library (gallery UI)?
│  └─ Requires PHPhotoLibrary authorization
│     └─ Request .readWrite for browsing
│     └─ Handle .limited status with presentLimitedLibraryPicker
│
├─ Save photos to camera roll?
│  └─ Requires PHPhotoLibrary authorization
│     └─ Request .addOnly (minimal) or .readWrite
│
└─ Just capture with camera?
   └─ Don't use PhotoKit - see camera-capture skill

2. Understand Permission Levels

Level	What It Allows	Request Method
No permission	User picks via system picker	PHPicker/PhotosPicker (automatic)
`.addOnly`	Save to camera roll only	`requestAuthorization(for: .addOnly)`
`.limited`	User-selected subset only	User chooses in system UI
`.authorized`	Full library access	`requestAuthorization(for: .readWrite)`

Key insight: PHPicker and PhotosPicker require NO permission. The system handles privacy.

3. Info.plist Keys

<!-- Required for any PhotoKit access -->
<key>NSPhotoLibraryUsageDescription</key>
<string>Access your photos to share them</string>

<!-- Required if saving photos -->
<key>NSPhotoLibraryAddUsageDescription</key>
<string>Save photos to your library</string>

Core Patterns

Pattern 1: SwiftUI PhotosPicker (iOS 16+)

Use case: Let users select photos in a SwiftUI app.

import SwiftUI
import PhotosUI

struct ContentView: View {
    @State private var selectedItem: PhotosPickerItem?
    @State private var selectedImage: Image?

    var body: some View {
        VStack {
            PhotosPicker(
                selection: $selectedItem,
                matching: .images  // Filter to images only
            ) {
                Label("Select Photo", systemImage: "photo")
            }

            if let image = selectedImage {
                image
                    .resizable()
                    .scaledToFit()
            }
        }
        .onChange(of: selectedItem) { _, newItem in
            Task {
                await loadImage(from: newItem)
            }
        }
    }

    private func loadImage(from item: PhotosPickerItem?) async {
        guard let item else {
            selectedImage = nil
            return
        }

        // Load as Data first (more reliable than Image)
        if let data = try? await item.loadTransferable(type: Data.self),
           let uiImage = UIImage(data: data) {
            selectedImage = Image(uiImage: uiImage)
        }
    }
}

Multi-selection:

@State private var selectedItems: [PhotosPickerItem] = []

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

Advanced Filters (iOS 15+/16+)

// Screenshots only
matching: .screenshots

// Screen recordings only
matching: .screenRecordings

// Slo-mo videos
matching: .sloMoVideos

// Cinematic videos (iOS 16+)
matching: .cinematicVideos

// Depth effect photos
matching: .depthEffectPhotos

// Bursts
matching: .bursts

// Compound filters with .any, .all, .not
// Videos AND Live Photos
matching: .any(of: [.videos, .livePhotos])

// All images EXCEPT screenshots
matching: .all(of: [.images, .not(.screenshots)])

// All images EXCEPT screenshots AND panoramas
matching: .all(of: [.images, .not(.any(of: [.screenshots, .panoramas]))])

Cost: 15 min implementation, no permissions required

Pattern 1b: Embedded PhotosPicker (iOS 17+)

Use case: Embed picker inline in your UI instead of presenting as sheet.

import SwiftUI
import PhotosUI

struct EmbeddedPickerView: View {
    @State private var selectedItems: [PhotosPickerItem] = []

    var body: some View {
        VStack {
            // Your content above picker
            SelectedPhotosGrid(items: selectedItems)

            // Embedded picker fills available space
            PhotosPicker(
                selection: $selectedItems,
                maxSelectionCount: 10,
                selectionBehavior: .continuous,  // Live updates as user taps
                matching: .images
            ) {
                // Label is ignored for inline style
                Text("Select")
            }
            .photosPickerStyle(.inline)  // Embed instead of present
            .photosPickerDisabledCapabilities([.selectionActions])  // Hide Add/Cancel buttons
            .photosPickerAccessoryVisibility(.hidden, edges: .all)  // Hide nav/toolbar
            .frame(height: 300)  // Control picker height
            .ignoresSafeArea(.container, edges: .bottom)  // Extend to bottom edge
        }
    }
}

Picker Styles:

Style	Description
`.presentation`	Default modal sheet
`.inline`	Embedded in your view hierarchy
`.compact`	Single row, minimal vertical space

Customization modifiers:

// Hide navigation/toolbar accessories
.photosPickerAccessoryVisibility(.hidden, edges: .all)
.photosPickerAccessoryVisibility(.hidden, edges: .top)  // Just navigation bar
.photosPickerAccessoryVisibility(.hidden, edges: .bottom)  // Just toolbar

// Disable capabilities (hides UI for them)
.photosPickerDisabledCapabilities([.search])  // Hide search
.photosPickerDisabledCapabilities([.collectionNavigation])  // Hide albums
.photosPickerDisabledCapabilities([.stagingArea])  // Hide selection review
.photosPickerDisabledCapabilities([.selectionActions])  // Hide Add/Cancel

// Continuous selection for live updates
selectionBehavior: .continuous

Privacy note: First time an embedded picker appears, iOS shows an onboarding UI explaining your app can only access selected photos. A privacy badge indicates the picker is out-of-process.

Pattern 2: UIKit PHPickerViewController (iOS 14+)

Use case: Photo selection in UIKit apps.

import PhotosUI

class PhotoPickerViewController: UIViewController, PHPickerViewControllerDelegate {

    func showPicker() {
        var config = PHPickerConfiguration()
        config.selectionLimit = 1  // 0 = unlimited
        config.filter = .images    // or .videos, .any(of: [.images, .videos])

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

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

        guard let result = results.first else { return }

        // Load image asynchronously
        result.itemProvider.loadObject(ofClass: UIImage.self) { [weak self] object, error in
            guard let image = object as? UIImage else { return }

            DispatchQueue.main.async {
                self?.displayImage(image)
            }
        }
    }
}

Filter options:

// Images only
config.filter = .images

// Videos only
config.filter = .videos

// Live Photos only
config.filter = .livePhotos

// Images and videos
config.filter = .any(of: [.images, .videos])

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

// iOS 16+ filters
config.filter = .cinematicVideos
config.filter = .depthEffectPhotos
config.filter = .bursts

UIKit Embedded Picker (iOS 17+)

// Configure for embedded use
var config = PHPickerConfiguration()
config.selection = .continuous  // Live updates instead of waiting for Add button
config.mode = .compact  // Single row layout (optional)
config.selectionLimit = 10

// Hide accessories
config.edgesWithoutContentMargins = .all  // No margins around picker

// Disable capabilities
config.disabledCapabilities = [.search, .selectionActions]

let picker = PHPickerViewController(configuration: config)
picker.delegate = self

// Add as child view controller (required for embedded)
addChild(picker)
containerView.addSubview(picker.view)
picker.view.frame = containerView.bounds
picker.didMove(toParent: self)

Updating picker while displayed (iOS 17+):

// Deselect assets by their identifiers
picker.deselectAssets(withIdentifiers: ["assetID1", "assetID2"])

// Reorder assets in selection
picker.moveAsset(withIdentifier: "assetID", afterAssetWithIdentifier: "otherID")

Cost: 20 min implementation, no permissions required

Pattern 2b: Options Menu & HDR Support (iOS 17+)

The picker now shows an Options menu letting users choose to strip location metadata from photos. This works automatically with PhotosPicker and PHPicker.

Preserving HDR content:

By default, picker may transcode to JPEG, losing HDR data. To receive original format:

// SwiftUI - Use .current encoding to preserve HDR
PhotosPicker(
    selection: $selectedItems,
    matching: .images,
    preferredItemEncoding: .current  // Don't transcode
) { ... }

// Loading with original format preservation
struct HDRImage: Transferable {
    let data: Data

    static var transferRepresentation: some TransferRepresentation {
        DataRepresentation(importedContentType: .image) { data in
            HDRImage(data: data)
        }
    }
}

// Request .image content type (generic) not .jpeg (specific)
let result = try await item.loadTransferable(type: HDRImage.self)

UIKit equivalent:

var config = PHPickerConfiguration()
config.preferredAssetRepresentationMode = .current  // Don't transcode

Cinematic mode videos: Picker returns rendered version with depth effects baked in. To get original with decision points, use PhotoKit with library access instead.

Pattern 3: Handling Limited Library Access

Use case: User granted limited access; let them add more photos.

Suppressing automatic prompt (iOS 14+):

By default, iOS shows "Select More Photos" prompt when .limited is detected. To handle it yourself:

<!-- Info.plist - Add this to handle limited access UI yourself -->
<key>PHPhotoLibraryPreventAutomaticLimitedAccessAlert</key>
<true/>

Manual limited access handling:

import Photos

class PhotoLibraryManager {

    func checkAndRequestAccess() async -> PHAuthorizationStatus {
        let status = PHPhotoLibrary.authorizationStatus(for: .readWrite)

        switch status {
        case .notDetermined:
            return await PHPhotoLibrary.requestAuthorization(for: .readWrite)

        case .limited:
            // User granted limited access - show UI to expand
            await presentLimitedLibraryPicker()
            return .limited

        case .authorized:
            return .authorized

        case .denied, .restricted:
            return status

        @unknown default:
            return status
        }
    }

    @MainActor
    func presentLimitedLibraryPicker() {
        guard let windowScene = UIApplication.shared.connectedScenes
            .first(where: { $0.activationState == .foregroundActive }) as? UIWindowScene,
              let rootVC = windowScene.windows.first?.rootViewController else {
            return
        }

        PHPhotoLibrary.shared().presentLimitedLibraryPicker(from: rootVC)
    }
}

Observe limited selection changes:

// Register for changes
PHPhotoLibrary.shared().register(self)

// In delegate
func photoLibraryDidChange(_ changeInstance: PHChange) {
    // User may have modified their limited selection
    // Refresh your photo grid
}

Cost: 30 min implementation

Pattern 4: Saving Photos to Camera Roll

Use case: Save captured or edited photos.

import Photos

func saveImageToLibrary(_ image: UIImage) async throws {
    // Request add-only permission (minimal access)
    let status = await PHPhotoLibrary.requestAuthorization(for: .addOnly)

    guard status == .authorized || status == .limited else {
        throw PhotoError.permissionDenied
    }

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

// With metadata preservation
func savePhotoData(_ data: Data, metadata: [String: Any]? = nil) async throws {
    try await PHPhotoLibrary.shared().performChanges {
        let request = PHAssetCreationRequest.forAsset()

        // Write data to temp file for addResource
        let tempURL = FileManager.default.temporaryDirectory
            .appendingPathComponent(UUID().uuidString)
            .appendingPathExtension("jpg")
        try? data.write(to: tempURL)

        request.addResource(with: .photo, fileURL: tempURL, options: nil)
    }
}

Cost: 15 min implementation

Pattern 5: Loading Images from PhotosPickerItem

Use case: Properly handle async image loading with error handling.

The problem: Default Image Transferable only supports PNG. Most photos are JPEG/HEIF.

// Custom Transferable for any image format
struct TransferableImage: 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 TransferableImage(image: image)
        }
    }

    enum TransferError: Error {
        case importFailed
    }
}

// Usage
func loadImage(from item: PhotosPickerItem) async -> UIImage? {
    do {
        let result = try await item.loadTransferable(type: TransferableImage.self)
        return result?.image
    } catch {
        print("Failed to load image: \(error)")
        return nil
    }
}

Loading with progress:

func loadImageWithProgress(from item: PhotosPickerItem) async -> UIImage? {
    let progress = Progress()

    return await withCheckedContinuation { continuation in
        _ = item.loadTransferable(type: TransferableImage.self) { result in
            switch result {
            case .success(let transferable):
                continuation.resume(returning: transferable?.image)
            case .failure:
                continuation.resume(returning: nil)
            }
        }
    }
}

Cost: 20 min implementation

Pattern 6: Observing Photo Library Changes

Use case: Keep your gallery UI in sync with Photos app.

import Photos

class PhotoGalleryViewModel: NSObject, ObservableObject, PHPhotoLibraryChangeObserver {
    @Published var photos: [PHAsset] = []

    private var fetchResult: PHFetchResult<PHAsset>?

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

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

    func fetchPhotos() {
        let options = PHFetchOptions()
        options.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        fetchResult = PHAsset.fetchAssets(with: .image, options: options)

        photos = fetchResult?.objects(at: IndexSet(0..<(fetchResult?.count ?? 0))) ?? []
    }

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

        DispatchQueue.main.async {
            self.fetchResult = changes.fetchResultAfterChanges
            self.photos = changes.fetchResultAfterChanges.objects(at:
                IndexSet(0..<changes.fetchResultAfterChanges.count)
            )
        }
    }
}

Cost: 30 min implementation

Anti-Patterns

Anti-Pattern 1: Requesting Full Access for Photo Picking

Wrong:

// Over-requesting - picker doesn't need this!
let status = await PHPhotoLibrary.requestAuthorization(for: .readWrite)
if status == .authorized {
    showPhotoPicker()
}

Right:

// Just show the picker - no permission needed
PhotosPicker(selection: $item, matching: .images) {
    Text("Select Photo")
}

Why it matters: PHPicker and PhotosPicker handle privacy automatically. Requesting library access when you only need to pick photos is a privacy violation and may cause App Store rejection.

Anti-Pattern 2: Ignoring Limited Status

Wrong:

let status = PHPhotoLibrary.authorizationStatus(for: .readWrite)
if status == .authorized {
    showGallery()
} else {
    showPermissionDenied()  // Wrong! .limited is valid
}

Right:

let status = PHPhotoLibrary.authorizationStatus(for: .readWrite)
switch status {
case .authorized:
    showGallery()
case .limited:
    showGallery()  // Works with limited selection
    showLimitedBanner()  // Explain to user
case .denied, .restricted:
    showPermissionDenied()
case .notDetermined:
    requestAccess()
@unknown default:
    break
}

Why it matters: iOS 14+ users can grant limited access. Treating it as denied frustrates users.

Anti-Pattern 3: Synchronous Image Loading

Wrong:

// Blocks UI thread
let data = try! selectedItem.loadTransferable(type: Data.self)

Right:

Task {
    if let data = try? await selectedItem.loadTransferable(type: Data.self) {
        // Use data
    }
}

Why it matters: Large photos (RAW, panoramas) take seconds to load. Blocking UI causes ANR.

Anti-Pattern 4: Using UIImagePickerController for Photo Selection

Wrong:

let picker = UIImagePickerController()
picker.sourceType = .photoLibrary
present(picker, animated: true)

Right:

var config = PHPickerConfiguration()
config.filter = .images
let picker = PHPickerViewController(configuration: config)
present(picker, animated: true)

Why it matters: UIImagePickerController is deprecated for photo selection. PHPicker is more reliable, handles large assets, and provides better privacy.

Pressure Scenarios

Scenario 1: "Just Get Photo Access Working"

Context: Product wants photo import feature. You're considering requesting full library access "to be safe."

Pressure: "Users will just tap Allow anyway."

Reality: Since iOS 14, users can grant limited access. Full access request triggers additional privacy prompt. App Store Review may reject unnecessary permission requests.

Correct action:

Use PhotosPicker or PHPicker (no permission needed)
Only request .readWrite if building a gallery browser
Only request .addOnly if just saving photos

Push-back template: "PHPicker works without any permission request - users can select photos directly. Requesting library access when we only need picking is a privacy violation that App Store Review may flag."

Scenario 2: "Users Say They Can't See Their Photos"

Context: Support tickets about "no photos available" even though user granted access.

Pressure: "Just ask for full access again."

Reality: User likely granted .limited access and selected 0 photos initially.

Correct action:

Check for .limited status
Show presentLimitedLibraryPicker() to let user add photos
Explain in UI: "Tap here to add more photos"

Push-back template: "The user has limited access - they need to expand their selection. I'll add a button that opens the limited library picker so they can add more photos."

Scenario 3: "Photo Loads Taking Forever"

Context: Users complain photo picker is slow to display selected images.

Pressure: "Can you cache or preload somehow?"

Reality: Large photos (RAW, panoramas, Live Photos) are slow to decode. Solution is UX, not caching.

Correct action:

Show loading placeholder immediately
Load thumbnail first, full image second
Show progress indicator for large files
Use async/await to avoid blocking

Push-back template: "Large photos take time to load - that's physics. I'll show a placeholder immediately and load progressively. For the picker UI, thumbnail loading is already optimized by the system."

Checklist

Before shipping photo library features:

Permission Strategy:

☑ Using PHPicker/PhotosPicker for simple selection (no permission needed)
☑ Only requesting .readWrite if building gallery UI
☑ Only requesting .addOnly if only saving photos
☑ Info.plist usage descriptions present

Limited Library:

☑ Handling .limited status (not treating as denied)
☑ Offering presentLimitedLibraryPicker() for users to add photos
☑ UI explains limited access to users

Image Loading:

☑ All loading is async (no UI blocking)
☑ Custom Transferable handles JPEG/HEIF (not just PNG)
☑ Error handling for failed loads
☑ Loading indicator for large files

Saving Photos:

☑ Using .addOnly when full access not needed
☑ Using performChanges for atomic operations
☑ Handling save failures gracefully

Photo Library Changes:

☑ Registered as PHPhotoLibraryChangeObserver if displaying library
☑ Updating UI on main thread after changes
☑ Unregistering observer in deinit

Resources

WWDC: 2020-10652, 2020-10641, 2022-10023, 2023-10107

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

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

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