Flutter Sticker Maker #

A cross-platform Flutter plugin to create stickers by removing backgrounds from images using iOS Vision/CoreImage and ONNX.

Features #

• iOS 17.0: Uses Vision and CoreImage with enhanced quality settings and edge smoothing
• Android and iOS below 17.0: Uses ONNX models for background removal
• Configurable border support with customizable color and width
• Simple Dart API
• Multiple visual effect styles (Classic, Sparkle, Burst, Flutter Overlay) that mirror across Flutter and SwiftUI implementations

Quality Enhancements #

• Image preprocessing: Automatic contrast and brightness enhancement
• Edge smoothing: Advanced algorithms to create natural-looking edges
• Noise reduction: Built-in filtering for cleaner results
• High-resolution support: Maintains image quality for large stickers

Performance Optimizations #

• Native FFI Processing: High-performance C/C++ implementation for mask processing operations
• SIMD Optimizations: ARM NEON (Android) and Accelerate Framework (iOS) for vectorized operations
• Optimized Algorithms: Separable Gaussian blur (O(n) vs O(n²)) and efficient distance transforms
• Memory Management: Memory pooling and zero-copy operations to reduce allocation overhead
• Expected Speedup: 2-5x faster sticker creation with 30-50% less memory usage

The native FFI optimization automatically falls back to pure Dart implementation if the native library is unavailable, ensuring compatibility across all platforms.

Usage #

alternatively, you can initialize the plugin with the following code:

FlutterStickerMaker.initialize();

and dispose it when done:

FlutterStickerMaker.dispose();

make a sticker from an image:

import 'package:flutter_sticker_maker/flutter_sticker_maker.dart';

// Basic usage
final sticker = await FlutterStickerMaker.makeSticker(imageBytes);

// With border customization
final stickerWithBorder = await FlutterStickerMaker.makeSticker(
  imageBytes,
  addBorder: true,
  borderColor: '#FF0000', // Red border
  borderWidth: 15.0,      // 15 pixel border width
);

// With visual effect (native on iOS 17+)
final stickerWithEffect = await FlutterStickerMaker.makeSticker(
  imageBytes,
  showVisualEffect: true, // Shows animated preview overlay
  speckleType: SpeckleType.classic, // Choose overlay style (classic, sparkle, burst, flutterOverlay)
);

// With Flutter overlay style on ONNX platforms (Android & older iOS)
final flutterOverlayPreview = await FlutterStickerMaker.makeSticker(
  imageBytes,
  showVisualEffect: true,
  speckleType: SpeckleType.flutterOverlay, // Flutter overlay style (ONNX platforms)
);

Parameters #

• imageBytes: The input image as Uint8List (PNG/JPEG)
• addBorder: Whether to add a border around the sticker (default: true)
• borderColor: Hex color string for the border (default: '#FFFFFF')
• borderWidth: Width of the border in pixels (default: 12.0)
• showVisualEffect: Whether to show the visual effect overlay during processing (native SwiftUI on iOS 17+, Flutter overlay everywhere else, default: false)
• speckleType: Selects the overlay style (SpeckleType.classic, sparkle, burst, or flutterOverlay). Defaults to classic. (the classic, sparkle, and burst styles match the native SwiftUI implementation on iOS 17+)
• visualEffectBuilder: Supply a VisualEffectBuilder to fully customize the overlay on every platform. The builder receives the source bytes and a VisualEffectRequest so you can await request.processing, call request.dismiss(), or keep the overlay visible after processing.

Visual Effect Feature #

When showVisualEffect is enabled:

• iOS 17+ (Vision mode) uses the native SwiftUI overlay with speckle emitters and mask reveal animation.
• ONNX platforms (Android & older iOS) now render a Flutter-based overlay with the same speckle styles, adaptive tinting, and sticker pop animation.
• The overlay automatically dismisses after processing finishes and gracefully falls back if no root overlay is available.
• Choose between SpeckleType.classic, sparkle, burst, or the new flutterOverlay style to force the gradient-only reveal that matches the Flutter implementation on every platform.
• Provide visualEffectBuilder when you need a custom progress or preview UI. It overrides the platform-specific overlays and gains direct control over when the overlay dismisses.

Custom Visual Effect Builder

final sticker = await FlutterStickerMaker.makeSticker(
  imageBytes,
  showVisualEffect: true, // optional when a builder is provided
  visualEffectBuilder: (context, request) {
    return ColoredBox(
      color: Colors.black54,
      child: Center(
        child: FutureBuilder<Uint8List?>(
          future: request.processing,
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              // Keep overlay up for a manual preview, then dismiss.
              request.keepOverlayUntilDismissed();
              return GestureDetector(
                onTap: request.dismiss,
                child: Image.memory(snapshot.data!, fit: BoxFit.contain),
              );
            }
            return const CircularProgressIndicator.adaptive();
          },
        ),
      ),
    );
  },
);

On platforms where overlays cannot be drawn (e.g., headless tests), the request still completes without animation.

Examples #

Demo App Screenshots #

See example/ for a full demo app.

Setup #

• iOS: Minimum iOS 16.0
• Android: Minimum SDK 24

Permissions #

Add to AndroidManifest.xml:

<uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" android:maxSdkVersion="32"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="28"/>
<uses-permission android:name="android.permission.CAMERA" />

Add to ios/Runner/Info.plist:

<key>NSPhotoLibraryUsageDescription</key>
<string>This app needs access to your photo library to pick images and save stickers.</string>
<key>NSCameraUsageDescription</key>
<string>This app needs camera access to take pictures for sticker creation.</string>
<key>NSPhotoLibraryAddUsageDescription</key>
<string>This app saves stickers to your photo library.</string>

Thanks #

Background removal: image_background_remover

SpoilerView effect: StickerViewExample