# Photokit

> Implement, review, or improve photo picking, camera capture, and media handling in iOS apps using PhotoKit and AVFoundation. Use when working with PhotosPicker, PHPickerViewController, camera capture sessions (AVCaptureSession), photo library access, image loading and display, video recording, or media permissions. Also use when selecting photos from the library, taking pictures, recording video, processing images, or handling photo/camera privacy permissions in Swift apps.

- Skill: `om-scogo/photokit` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds add om-scogo/photokit`
- Raw SKILL.md: https://api.skillmd.com/api/skills/om-scogo/photokit/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: om-scogo (https://skillmd.com/u/om-scogo)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/om-scogo/photokit

---


# PhotoKit

Modern patterns for photo picking, camera capture, image loading, and media permissions targeting iOS 26+ with Swift 6.3. Patterns are backward-compatible to iOS 16 unless noted. See [references/photokit-patterns.md](references/photokit-patterns.md) for complete picker recipes and [references/camera-capture.md](references/camera-capture.md) for AVCaptureSession patterns.

## Contents

- [PhotosPicker (SwiftUI, iOS 16+)](#photospicker-swiftui-ios-16)
- [Privacy and Permissions](#privacy-and-permissions)
- [Camera Capture Basics](#camera-capture-basics)
- [Image Loading and Display](#image-loading-and-display)
- [Common Mistakes](#common-mistakes)
- [Review Checklist](#review-checklist)
- [References](#references)

## PhotosPicker (SwiftUI, iOS 16+)

`PhotosPicker` is the native SwiftUI replacement for `UIImagePickerController`. It runs out-of-process, requires no photo library permission for browsing, and supports single or multi-selection with media type filtering.

### Single Selection

```swift
import SwiftUI
import PhotosUI

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

    var body: some View {
        VStack {
            if let selectedImage {
                selectedImage
                    .resizable()
                    .scaledToFit()
                    .frame(maxHeight: 300)
            }

            PhotosPicker("Select Photo", selection: $selectedItem, matching: .images)
        }
        .onChange(of: selectedItem) { _, newItem in
            Task {
                if let data = try? await newItem?.loadTransferable(type: Data.self),
                   let uiImage = UIImage(data: data) {
                    selectedImage = Image(uiImage: uiImage)
                }
            }
        }
    }
}
```

### Multi-Selection

```swift
struct MultiPhotoPicker: View {
    @State private var selectedItems: [PhotosPickerItem] = []
    @State private var selectedImages: [Image] = []

    var body: some View {
        VStack {
            ScrollView(.horizontal) {
                HStack {
                    ForEach(selectedImages.indices, id: \.self) { index in
                        selectedImages[index]
                            .resizable()
                            .scaledToFill()
                            .frame(width: 100, height: 100)
                            .clipShape(.rect(cornerRadius: 8))
                    }
                }
            }

            PhotosPicker(
                "Select Photos",
                selection: $selectedItems,
                maxSelectionCount: 5,
                matching: .images
            )
        }
        .onChange(of: selectedItems) { _, newItems in
            Task {
                selectedImages = []
                for item in newItems {
                    if let data = try? await item.loadTransferable(type: Data.self),
                       let uiImage = UIImage(data: data) {
                        selectedImages.append(Image(uiImage: uiImage))
                    }
                }
            }
        }
    }
}
```

### Media Type Filtering

Filter with `PHPickerFilter` composites to restrict selectable media:

```swift
// Images only
PhotosPicker(selection: $items, matching: .images)

// Videos only
PhotosPicker(selection: $items, matching: .videos)

// Live Photos only
PhotosPicker(selection: $items, matching: .livePhotos)

// Screenshots only
PhotosPicker(selection: $items, matching: .screenshots)

// Images and videos combined
PhotosPicker(selection: $items, matching: .any(of: [.images, .videos]))

// Images excluding screenshots
PhotosPicker(selection: $items, matching: .all(of: [.images, .not(.screenshots)]))
```

### Loading Selected Items with Transferable

`PhotosPickerItem` loads content asynchronously via `loadTransferable(type:)`. Define a `Transferable` type for automatic decoding:

```swift
struct PickedImage: Transferable {
    let data: Data
    let image: Image

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

enum TransferError: Error {
    case importFailed
}

// Usage
if let picked = try? await item.loadTransferable(type: PickedImage.self) {
    selectedImage = picked.image
}
```

Always load in a `Task` to avoid blocking the main thread. Handle `nil` returns and thrown errors -- the user may select a format that cannot be decoded.

## Privacy and Permissions

### Photo Library Access Levels

iOS provides two access levels for the photo library. The system automatically presents the limited-library picker when an app requests `.readWrite` access -- users choose which photos to share.

| Access Level | Description | Info.plist Key |
|-------------|-------------|----------------|
| Add-only | Write photos to the library without reading | `NSPhotoLibraryAddUsageDescription` |
| Read-write | Full or limited read access plus write | `NSPhotoLibraryUsageDescription` |

`PhotosPicker` requires no permission to browse -- it runs out-of-process and only grants access to selected items. Request explicit permission only when you need to read the full library (e.g., a custom gallery) or save photos.

### Checking and Requesting Photo Library Permission

```swift
import Photos

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

    switch status {
    case .notDetermined:
        return await PHPhotoLibrary.requestAuthorization(for: .readWrite)
    case .authorized, .limited:
        return status
    case .denied, .restricted:
        return status
    @unknown default:
        return status
    }
}
```

### Camera Permission

Add `NSCameraUsageDescription` to Info.plist. Check and request access before configuring a capture session:

```swift
import AVFoundation

func requestCameraAccess() async -> Bool {
    let status = AVCaptureDevice.authorizationStatus(for: .video)

    switch status {
    case .notDetermined:
        return await AVCaptureDevice.requestAccess(for: .video)
    case .authorized:
        return true
    case .denied, .restricted:
        return false
    @unknown default:
        return false
    }
}
```

### Handling Denied Permissions

When the user denies access, guide them to Settings. Never repeatedly prompt or hide functionality silently.

```swift
struct PermissionDeniedView: View {
    let message: String
    @Environment(\.openURL) private var openURL

    var body: some View {
        ContentUnavailableView {
            Label("Access Denied", systemImage: "lock.shield")
        } description: {
            Text(message)
        } actions: {
            Button("Open Settings") {
                if let url = URL(string: UIApplication.openSettingsURLString) {
                    openURL(url)
                }
            }
        }
    }
}
```

### Required Info.plist Keys

| Key | When Required |
|-----|--------------|
| `NSPhotoLibraryUsageDescription` | Reading photos from the library |
| `NSPhotoLibraryAddUsageDescription` | Saving photos/videos to the library |
| `NSCameraUsageDescription` | Accessing the camera |
| `NSMicrophoneUsageDescription` | Recording audio (video with sound) |

Omitting a required key causes a runtime crash when the permission dialog would appear.

## Camera Capture Basics

Own each capture session in a dedicated controller and serialize configuration, `startRunning()`, and `stopRunning()` on the same non-main executor. Never mix main-actor configuration with detached start/stop tasks: `beginConfiguration()`/`commitConfiguration()` and session state changes must not race. The representable view only displays the preview.

### Minimal Camera Manager

Load [Camera Capture](references/camera-capture.md) for the serialized-controller pattern, photo/video delegates, focus, torch, orientation, and scanning. The critical lifecycle is:

1. Request access outside the session configuration transaction.
2. On the capture executor, call `beginConfiguration()` and immediately install `defer { commitConfiguration() }` so every early exit balances the transaction.
3. Add inputs and outputs only after `canAddInput`/`canAddOutput` checks.
4. Start or stop on that same executor, then publish UI state on the main actor only after the synchronous call returns.
5. On failure, stop, restore a fresh session fixture, fix the configuration, and rerun authorization, background/foreground, interruption, and capture checks.

### Camera Preview in SwiftUI

Wrap `AVCaptureVideoPreviewLayer` in a `UIViewRepresentable`. Override `layerClass` for automatic resizing:

```swift
import SwiftUI
import AVFoundation

struct CameraPreview: UIViewRepresentable {
    let session: AVCaptureSession

    func makeUIView(context: Context) -> PreviewView {
        let view = PreviewView()
        view.previewLayer.session = session
        view.previewLayer.videoGravity = .resizeAspectFill
        return view
    }

    func updateUIView(_ uiView: PreviewView, context: Context) {
        if uiView.previewLayer.session !== session {
            uiView.previewLayer.session = session
        }
    }
}

final class PreviewView: UIView {
    override class var layerClass: AnyClass { AVCaptureVideoPreviewLayer.self }
    var previewLayer: AVCaptureVideoPreviewLayer { layer as! AVCaptureVideoPreviewLayer }
}
```

### Using the Camera in a View

```swift
struct CameraScreen: View {
    @State private var cameraManager = CameraManager()

    var body: some View {
        ZStack(alignment: .bottom) {
            CameraPreview(session: cameraManager.session)
                .ignoresSafeArea()

            Button {
                // Capture photo -- see references/camera-capture.md
            } label: {
                Circle()
                    .fill(.white)
                    .frame(width: 72, height: 72)
                    .overlay(Circle().stroke(.gray, lineWidth: 3))
            }
            .padding(.bottom)
        }
        .task {
            await cameraManager.configure()
            cameraManager.start()
        }
        .onDisappear {
            cameraManager.stop()
        }
    }
}
```

Always call `stop()` in `onDisappear`. A running capture session holds the camera exclusively and drains battery.

## Image Loading and Display

### AsyncImage for Remote Images

```swift
AsyncImage(url: imageURL) { phase in
    switch phase {
    case .empty:
        ProgressView()
    case .success(let image):
        image
            .resizable()
            .scaledToFill()
    case .failure:
        Image(systemName: "photo")
            .foregroundStyle(.secondary)
    @unknown default:
        EmptyView()
    }
}
.frame(width: 200, height: 200)
.clipShape(.rect(cornerRadius: 12))
```

`AsyncImage` does not cache images across view redraws. For production apps with many images, use a dedicated image loading library or `URLCache`-based caching.

### Downsampling Large Images

Load full-resolution photos from the library into a display-sized `CGImage` to avoid memory spikes. A 48MP photo can consume over 200 MB uncompressed.

```swift
import ImageIO
import UIKit

func downsample(data: Data, to pointSize: CGSize, scale: CGFloat = UITraitCollection.current.displayScale) -> UIImage? {
    let maxDimensionInPixels = max(pointSize.width, pointSize.height) * scale

    let options: [CFString: Any] = [
        kCGImageSourceCreateThumbnailFromImageAlways: true,
        kCGImageSourceShouldCacheImmediately: true,
        kCGImageSourceCreateThumbnailWithTransform: true,
        kCGImageSourceThumbnailMaxPixelSize: maxDimensionInPixels
    ]

    guard let source = CGImageSourceCreateWithData(data as CFData, nil),
          let cgImage = CGImageSourceCreateThumbnailAtIndex(source, 0, options as CFDictionary) else {
        return nil
    }

    return UIImage(cgImage: cgImage)
}
```

Use this whenever displaying user-selected photos in lists, grids, or thumbnails. Pass the raw `Data` from `PhotosPickerItem` directly to the downsampler before creating a `UIImage`.

### Image Rendering Modes

```swift
// Original: display the image as-is with its original colors
Image("photo")
    .renderingMode(.original)

// Template: treat the image as a mask, colored by foregroundStyle
Image(systemName: "heart.fill")
    .renderingMode(.template)
    .foregroundStyle(.red)
```

Use `.original` for photos and artwork. Use `.template` for icons that should adopt the current tint color.

## Common Mistakes

**DON'T:** Use `UIImagePickerController` for photo picking.
**DO:** Use `PhotosPicker` (SwiftUI) or `PHPickerViewController` (UIKit).
*Why:* `UIImagePickerController` is legacy API with limited functionality. `PhotosPicker` runs out-of-process, supports multi-selection, and requires no library permission for browsing.

**DON'T:** Request full photo library access when you only need the user to pick photos.
**DO:** Use `PhotosPicker` which requires no permission, or request `.readWrite` and let the system handle limited access.
*Why:* Full access is unnecessary for most pick-and-use workflows. The system's limited-library picker respects user privacy and still grants access to selected items.

**DON'T:** Load full-resolution images into memory for thumbnails.
**DO:** Use `CGImageSource` with `kCGImageSourceThumbnailMaxPixelSize` to downsample. A 48MP image is over 200 MB uncompressed.

**DON'T:** Block the main thread loading `PhotosPickerItem` data.
**DO:** Use `async loadTransferable(type:)` in a `Task`.

**DON'T:** Forget to stop `AVCaptureSession` when the view disappears.
**DO:** Call `session.stopRunning()` in `onDisappear` or `dismantleUIView`.

**DON'T:** Assume camera access is granted without checking.
**DO:** Check `AVCaptureDevice.authorizationStatus(for: .video)` and handle `.denied`/`.restricted`.

**DON'T:** Call `session.startRunning()` on the main thread.
**DO:** Run it on the same dedicated serial executor that owns configuration and stop operations.
*Why:* `startRunning()` is a synchronous blocking call that can take hundreds of milliseconds while the hardware initializes.

**DON'T:** Create `AVCaptureSession` inside a `UIViewRepresentable`.
**DO:** Own the session in a separate `@Observable` model.

## Review Checklist

- [ ] `PhotosPicker` used instead of deprecated `UIImagePickerController`
- [ ] Privacy descriptions in Info.plist for camera/photo library
- [ ] Loading states handled for async image/video loading
- [ ] Large images downsampled with `CGImageSource` before display
- [ ] Camera session started on background thread; stopped in `onDisappear`
- [ ] Permission denial handled with Settings deep link
- [ ] `AVCaptureSession` owned by model, not created inside `UIViewRepresentable`
- [ ] Media asset types and picker results are `Sendable` across concurrency boundaries

## References

- [references/photokit-patterns.md](references/photokit-patterns.md) — Picker patterns, media loading, HEIC handling
- [references/camera-capture.md](references/camera-capture.md) — AVCaptureSession, photo/video capture, QR scanning
- [references/image-loading-caching.md](references/image-loading-caching.md) — AsyncImage, caching, downsampling
- [references/av-playback.md](references/av-playback.md) — AVPlayer, streaming, audio