photos-camera-media
"Implement, review, or improve photo picking, camera capture, and media handling in iOS apps. 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
npx skills add dpearson2699/swift-ios-skills --skill photos-camera-mediaBefore / After 效果对比
0 组description 文档
name: photos-camera-media description: "Implement, review, or improve photo picking, camera capture, and media handling in iOS apps. 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."
Photos, Camera & Media
Modern patterns for photo picking, camera capture, image loading, and media permissions targeting iOS 26+ with Swift 6.2. Patterns are backward-compatible to iOS 16 unless noted.
See references/photospicker-patterns.md for complete picker recipes and references/camera-capture.md for AVCaptureSession patterns.
Contents
- PhotosPicker (SwiftUI, iOS 16+)
- Privacy and Permissions
- Camera Capture Basics
- Image Loading and Display
- Common Mistakes
- Review Checklist
- 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
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
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(RoundedRectangle(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:
// 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:
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
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:
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.
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
Manage camera sessions in a dedicated @Observable model. The representable view only displays the preview. See references/camera-capture.md for complete patterns.
Minimal Camera Manager
import AVFoundation
@available(iOS 17.0, *)
@Observable
@MainActor
final class CameraManager {
let session = AVCaptureSession()
private let photoOutput = AVCapturePhotoOutput()
private var currentDevice: AVCaptureDevice?
var isRunning = false
var capturedImage: Data?
func configure() async {
guard await requestCameraAccess() else { return }
session.beginConfiguration()
session.sessionPreset = .photo
// Add camera input
guard let device = AVCaptureDevice.default(.builtInWideAngleCamera,
for: .video,
position: .back) else { return }
currentDevice = device
guard let input = try? AVCaptureDeviceInput(device: device),
session.canAddInput(input) else { return }
session.addInput(input)
// Add photo output
guard session.canAddOutput(photoOutput) else { return }
session.addOutput(photoOutput)
session.commitConfiguration()
}
func start() {
guard !session.isRunning else { return }
Task.detached { [session] in
session.startRunning()
}
isRunning = true
}
func stop() {
guard session.isRunning else { return }
Task.detached { [session] in
session.stopRunning()
}
isRunning = false
}
private func requestCameraAccess() async -> Bool {
let status = AVCaptureDevice.authorizationStatus(for: .video)
if status == .notDetermined {
return await AVCaptureDevice.requestAccess(for: .video)
}
return status == .authorized
}
}
Start and stop AVCaptureSession on a background queue. The startRunning() and stopRunning() methods are synchronous and block the calling thread.
Camera Preview in SwiftUI
Wrap AVCaptureVideoPreviewLayer in a UIViewRepresentable. Override layerClass for automatic resizing:
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
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, 32)
}
.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
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(RoundedRectangle(cornerRadius: 12))
AsyncImage does not cache images across view redraws. For production apps with many images, use a dedicated image loading library or implement 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.
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
// 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: Dispatch to a background thread with Task.detached or a dedicated serial queue.
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
- [ ]
PhotosPickerused instead of deprecatedUIImagePickerController - [ ] Privacy descriptions in Info.plist for camera/photo library
- [ ] Loading states handled for async image/video loading
- [ ] Large images downsampled with
CGImageSourcebefore display - [ ] Camera session started on background thread; stopped in
onDisappear - [ ] Permission denial handled with Settings deep link
- [ ]
AVCaptureSessionowned by model, not created insideUIViewRepresentable - [ ] Media asset types and picker results are
Sendablewhen passed across concurrency boundaries
References
references/photospicker-patterns.md— Picker patterns, media loading, HEIC handlingreferences/camera-capture.md— AVCaptureSession, photo/video capture, QR scanningreferences/image-loading-caching.md— AsyncImage, caching, downsamplingreferences/av-playback.md— AVPlayer, streaming, audio session, background audio
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