live_beauty_filter #

A Flutter plugin for iOS that applies a real-time milky/soft beauty filter to the live camera feed, entirely on the GPU. Built on AVFoundation + CoreImage + Metal — zero CPU pixel processing.

Features #

• Live camera preview with milky filter applied in real-time
• GPU-only pipeline — no frame drops, no battery drain from CPU processing
• Adjustable filter intensity at runtime (0.0 → 1.0)
• Front camera with correct mirroring and portrait orientation
• Zero-copy frame delivery to Flutter via Texture widget
• Filter chain: Gaussian blur → Bloom/Glow → Color grade (brightness + contrast lift)

Platform support #

Installation #

This is a local plugin — add it to your pubspec.yaml:

dependencies:
  live_beauty_filter:
    path: ../live_beauty_filter

Add camera permission to your app's ios/Runner/Info.plist:

<key>NSCameraUsageDescription</key>
<string>Camera is used for the live beauty filter preview.</string>

Plugin registration is automatic via Flutter's GeneratedPluginRegistrant — no AppDelegate.swift changes needed.

Usage #

Basic live preview #

import 'package:live_beauty_filter/live_beauty_filter.dart';

class CameraScreen extends StatefulWidget {
  const CameraScreen({super.key});

  @override
  State<CameraScreen> createState() => _CameraScreenState();
}

class _CameraScreenState extends State<CameraScreen> {
  final _controller = MilkyFilterController();

  @override
  void initState() {
    super.initState();
    _controller.initialize().then((_) => setState(() {}));
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    if (!_controller.isInitialized) {
      return const Center(child: CircularProgressIndicator());
    }
    return Texture(textureId: _controller.textureId!);
  }
}

Adjusting filter intensity #

// intensity: 0.0 = no filter, 1.0 = full milky
await _controller.setFilterIntensity(0.7);

Drop-in widget with built-in intensity slider #

MilkyCameraView()

How the filter works #

The milky look is achieved by chaining three CoreImage GPU passes on every frame:

CVPixelBuffer (raw frame)
    │
    ▼
CIGaussianBlur          — light softening (radius scales with intensity)
    │
    ▼
Bloom / Screen blend    — blurred copy composited over original for glow
    │
    ▼
CIColorControls         — brightness +, contrast -, saturation slight -
    │
    ▼
CIColorPolynomial       — raises black point (lifted shadows, milky whites)
    │
    ▼
CVPixelBuffer (filtered) → FlutterTexture → Texture() widget

All operations run on the Metal GPU via a CIContext created with useSoftwareRenderer: false. Frames are pooled with CVPixelBufferPool to eliminate per-frame heap allocation.

API reference #

MilkyFilterController #

MilkyFilterPipeline (iOS internal) #

Tuning the filter #

Edit the constants in MilkyFilterPipeline.swift to adjust the look:

// MilkyFilterPipeline.swift

// Blur softness (max radius at intensity 1.0)
let blurRadius = Double(intensity) * 4.0          // increase for dreamier blur

// Bloom strength (how much glow blends back in)
let bloomStrength = Double(intensity) * 0.45      // increase for stronger glow

// Color grade
let brightnessBoost      = Double(intensity) * 0.08   // raise for brighter
let contrastReduction    = 1.0 - Double(intensity) * 0.15  // lower = flatter/milkier
let saturationReduction  = 1.0 - Double(intensity) * 0.12  // lower = more faded

// Blue channel lift in CIColorPolynomial
// inputBlueCoefficients: CIVector(x: intensity * 0.06, ...)
// Increase x for a cooler (more blue-white) milky tone
// Decrease for a warmer tone

Testing #

Integration tests must run on a physical device — the camera does not work on Simulator.

Grant camera permission by running the example app once manually first:

cd example
flutter run -d <your-device-id>

Then run the integration tests:

flutter test integration_test/plugin_integration_test.dart -d <your-device-id>

Expected output:

+2: All tests passed!

Requirements #

• iOS 14.0+
• Xcode 14+
• A physical device (camera does not work on Simulator)
• Swift 5.7+

File structure #

live_beauty_filter/
├── ios/
│   ├── Classes/
│   │   ├── LiveBeautyFilterPlugin.swift      # Flutter plugin entry + MethodChannel
│   │   ├── MilkyCameraController.swift       # AVCapture session + frame delivery
│   │   └── MilkyFilterPipeline.swift         # CIFilter GPU chain (blur + bloom + grade)
│   ├── Resources/
│   │   └── PrivacyInfo.xcprivacy             # App Store privacy manifest
│   └── live_beauty_filter.podspec
├── lib/
│   ├── live_beauty_filter.dart               # Barrel export (main entry point)
│   ├── milky_filter_controller.dart          # MethodChannel Dart wrapper
│   ├── milky_camera_view.dart                # Drop-in Flutter widget with slider
│   ├── live_beauty_filter_platform_interface.dart
│   └── live_beauty_filter_method_channel.dart
├── example/
│   ├── lib/
│   │   └── main.dart                         # Example app — fullscreen filter preview
│   ├── integration_test/
│   │   └── plugin_integration_test.dart      # Integration tests (run on physical device)
│   └── ios/
│       └── Runner/
│           └── Info.plist                    # Must contain NSCameraUsageDescription
├── pubspec.yaml
└── README.md

License #

This project is licensed under the MIT License see the LICENSE file for details.