Prism

Camera pipeline Swift Package for iOS 18+, built on Swift 6.2 strict concurrency.

• Actor-isolated AVCaptureSession with a @MainActor facade and AsyncStream event delivery.
• Async/await capture: still, Live Photo, Portrait, burst, long-exposure night composite, video.
• Full manual surface: exposure / ISO / shutter / lens position / focus / white balance / HDR / low-light / frame rate / stabilization.
• iOS 17 AVCaptureDevice.RotationCoordinator, iOS 17/18 photo features (responsive capture, deferred photo delivery, zero shutter lag).
• Metal-backed Core Image filter pipeline with 20 built-in filters and correct per-filter intensity blending via CIBlendWithMask.
• Metal preview view + UIKit components (shutter, focus, grid, level, aspect mask, settings drawer).

Installation

Swift Package Manager — add Prism in Xcode (File → Add Package Dependencies…) or in Package.swift:

dependencies: [
    .package(url: "https://github.com/luminoid/Prism.git", from: "0.1.0"),
],
targets: [
    .target(
        name: "YourApp",
        dependencies: [
            .product(name: "PrismCore", package: "Prism"),
            .product(name: "PrismUI",   package: "Prism"), // optional, UIKit + Metal preview
        ]
    ),
]

Requires iOS 18+, Swift 6.2.

Architecture

PrismCore  Camera (PRMCameraActor + PRMCamera facade), capture helpers,
           AVCaptureDevice extensions, filter pipeline, utilities. No UI.

PrismUI    Metal preview view + UIKit camera components.
           Depends on PrismCore. `defaultIsolation(MainActor)`. No SnapKit.

Sources/PrismCore/
├── Camera/      PRMCameraActor, PRMCamera (+Observers), PRMCameraSession (+Format),
│                PRMCameraConfiguration, PRMCameraDevice, PRMCameraState,
│                PRMRotationCoordinator, PRMPermissions, PRMSessionError
├── Capture/     PRMPhotoCapture (still / Live / Portrait / burst, async),
│                PRMPhotoSettings, PRMPhoto, PRMLivePhoto, PRMPortraitPhoto,
│                PRMNightModeCapture, PRMVideoRecorder + PRMRecording, PRMDepthCapture
├── Device/      AVCaptureDevice +Zoom/Torch/Exposure/WhiteBalance/FrameRate/
│                ISO/Lens/HDR/Depth/Configuration, AVCaptureConnection+Stabilization,
│                PRMLens
├── Filter/      PRMFilter, PRMFilterRenderer, PRMBasicFilterRenderer, PRMFilterChain,
│                PRMFilterPipeline, PRMBufferPoolAllocator, PRMRenderContext,
│                PRMVideoFrame, Filters/{Color,Blur,Stylize,Distortion,PortraitBokeh}
└── Utilities/   PRMLogger, PRMStreamRegistry, PRMTempFile, PRMImage

Sources/PrismUI/
├── Preview/     PRMPreviewView + Shaders/PassThrough.metal
└── Components/  PRMShutterButton, PRMFocusIndicatorView, PRMGridView,
                 PRMLevelIndicatorView, PRMAspectRatioMaskView, PRMCaptureEventHelper,
                 PRMSettingsDrawerView, PRMSettingsRow

Features

Camera & capture

• Actor-isolated session — @PRMCameraActor serializes every AVCaptureSession mutation; PRMCamera is the @MainActor facade with AsyncStream<PRMCameraState> / errorStream / interruptionStream.
• Async/await capture — try await camera.capturePhoto(settings:) → PRMPhoto; captureLivePhoto(settings:) → PRMLivePhoto (still + paired movie URL); capturePortraitPhoto(settings:) → PRMPortraitPhoto (still + depth + portrait effects matte); captureBurst(count:settings:) → [PRMPhoto]; PRMVideoRecorder.start() / stop() → PRMRecording.
• Night mode — PRMNightModeCapture(capture:context:).capture(frameCount:perFrameDuration:iso:) averages N captures into a long-exposure composite.
• Manual controls — prm_setZoom, prm_setTorch, prm_setExposureBias, prm_setExposureMode, prm_setCustomExposure, prm_setISO, prm_setShutterSpeed, prm_setLensPosition, prm_setFocusMode, prm_lockWhiteBalance, prm_setFrameRate, prm_setVideoHDR, prm_setLowLightBoost, prm_setStabilization. All surface on PRMCamera as await camera.setX(...).
• Rotation coordinator — iOS 17+ AVCaptureDevice.RotationCoordinator exposed as AsyncStream<CGFloat> for preview + capture angles.
• Permissions — async PRMPermissions.requestCameraAccess() / requestMicrophoneAccess().
• iOS 17/18 photo features — enableResponsiveCapture, enableAutoDeferredPhotoDelivery, enableZeroShutterLag, enableLivePhoto, enableDepthDataDelivery, enablePortraitEffectsMatteDelivery, preferredVideoStabilizationMode.
• Runtime format swap — await camera.setHighResolutionPhotoFormat(true) promotes activeFormat to the 48MP-capable format on iPhone 14 Pro+ / 15 Pro+ wide camera (auxiliary delivery flags reconciled per Apple dev-forum 715452); await camera.enableDepthFormat() swaps to a depth-capable format for Portrait so depth ancillaries arrive populated.
• Multitasking camera access — iPad opt-in via enableMultitaskingCameraAccess.
• Lens descriptors — PRMLens exposes raw 35mm-equivalent focal length per physical camera; opt-in snapping(to:tolerance:) for marketing-friendly values.

Filter pipeline

• Value-type PRMFilter — Sendable protocol, func render(_ image: CIImage) -> CIImage. No AnyObject requirement.
• Shared render context — one Metal-backed CIContext per PRMFilterPipeline with .cacheIntermediates: false (per WWDC '20).
• PRMFilterPipeline — AVCaptureVideoDataOutputSampleBufferDelegate delivering frames via callback or AsyncStream<PRMVideoFrame>. discardsLateVideoFrames = true.
• PRMFilterChain — correct per-filter intensity blending using CIBlendWithMask against the previous step's output (fixes a subtle bug present in many filter-stack implementations).
• 20 built-in filters — Color: Brightness, Contrast, Saturation, HueRotation, Grayscale, Sepia, Vignette. Blur: Gaussian, Motion, Zoom. Stylize: Pixellate, Comic, Pointillize, Edges. Distortion: Bump, Twirl, Pinch, Vortex. Plus PortraitBokeh (matte- or depth-driven CIDepthBlurEffect) and PassThrough.

PrismUI

• PRMPreviewView — MTKView with lock-protected latest-frame buffer drawn on the display link, no per-frame Task / MainActor hop.
• PRMSettingsDrawerView — trailing-edge slide-in drawer with sectioned scroll and collapsible PRMSettingsRow controls.
• PRMShutterButton — photo / video / recording-active modes, tap + long-press.
• PRMFocusIndicatorView — animated tap-to-focus square, Reduce Motion aware.
• PRMGridView — rule of thirds, golden ratio, crosshair, Fibonacci spiral.
• PRMAspectRatioMaskView — 4:3 / 16:9 / 1:1 / full frame letterbox.
• PRMLevelIndicatorView — CoreMotion gravity-based horizon, hysteresis + snap-to-zero.
• PRMCaptureEventHelper — iOS 17.2+ AVCaptureEventInteraction wrapper for the Camera Control + volume buttons.

Quick start

import PrismCore
import PrismUI

@MainActor
final class CameraVC: UIViewController {
    private let camera = PRMCamera()
    private lazy var renderContext = PRMRenderContext()!
    private lazy var pipeline = PRMFilterPipeline(context: renderContext)
    private lazy var preview = PRMPreviewView(context: renderContext)

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(preview)
        preview.frame = view.bounds
        preview.autoresizingMask = [.flexibleWidth, .flexibleHeight]

        Task {
            guard await PRMPermissions.requestCameraAccess() else { return }
            try await camera.configure(PRMCameraConfiguration())
            await camera.session.setVideoDataOutputDelegate(pipeline)
            pipeline.onFrame = { [weak self] frame in
                self?.preview.update(frame.pixelBuffer)
            }
            await camera.start()
        }
    }
}

See Example/Sources/StudioViewController.swift for the full DSLR-grade integration.

Example app

Example/PrismExample.xcodeproj (XcodeGen) ships three demo screens:

1. Permissions — camera + microphone status pills and request flow.
2. Studio — DSLR-grade camera: preview, lens picker (35mm-equivalent), tap-to-focus, pinch-to-zoom, vertical drag for exposure bias, top-bar toggles (torch / grid / aspect / timer / burst / settings), telemetry strip (mode, zoom, ISO, shutter, EV, WB, frame rate), mode strip with PHOTO / LIVE / PORTRAIT / PANO / VIDEO / SLO-MO / NIGHT, and a slide-in settings drawer covering every supported AVFoundation API.
3. Filter Chain — real-time multi-filter editor with reorderable active pills, per-filter intensity sheet, and a library tabbed by category.

Studio	Settings drawer	Filter chain

Regenerate the Xcode project:

cd Example && xcodegen generate

The Example app uses SnapKit for its own layout — it is a private demo dependency, not a library one. Prism itself has no external SPM dependencies.

Build & test

xcodebuild build -scheme Prism-Package -destination 'platform=iOS Simulator,name=iPhone 17,OS=26.2' CODE_SIGNING_ALLOWED=NO
xcodebuild test  -scheme Prism-Package -destination 'platform=iOS Simulator,name=iPhone 17,OS=26.2' CODE_SIGNING_ALLOWED=NO

make check   # SwiftLint + SwiftFormat

Device-touching paths (AVCaptureDevice extensions, photo / video / depth capture start-stop) can't run on simulator because AVCaptureDevice.default(for: .video) returns nil. Those modules are covered via value-type tests, API-surface KeyPath locks, and Sendable round-trip checks. Hardware paths exercise via the Example app and the manual test plan.

Stats

Metric	Count
Source files	58 Swift + 1 Metal
PrismCore	49 files
PrismUI	9 files
Tests	142 across 44 suites
Built-in filters	20
Example screens	3

Privacy manifest (for consuming apps)

Prism does not ship a PrivacyInfo.xcprivacy — Apple aggregates privacy reports at the app bundle level, so the manifest belongs in the consuming app. Add the following to your app's PrivacyInfo.xcprivacy:

API category	Reason code	Why
NSPrivacyAccessedAPICategoryFileTimestamp	C617.1	PRMTempFile reads attributes (duration, size) of video files it writes.
NSPrivacyAccessedAPICategoryDiskSpace	85F4.1	Only if your app gates recording on available disk space; Prism itself does not read disk space.

Info.plist keys: NSCameraUsageDescription (always), NSMicrophoneUsageDescription (if includesAudio: true), NSPhotoLibraryAddUsageDescription (if you save captures via PHPhotoLibrary — Prism itself returns Data / URL and never touches PHPhotoLibrary).

Prism does not access UserDefaults, system boot time, or active keyboards, so those categories don't apply.

License

MIT — see LICENSE.