flutter_canvas_watermark #

Hardware-accelerated dynamic forensic canvas DRM watermark overlay for Flutter video streams, confidential documents, and screen recording protection.

Developed by Huot Lysokheng (Mobile Team Lead at Codingate & WebRTC Architect).

⚡️ Need a Full Production WebRTC SFU Audio/Video Calling Kit? #

Building a telehealth, education, or enterprise conferencing app with anti-leak protection?
Watermarking is one piece of the puzzle. If you need a complete, production-grade WebRTC infrastructure that replaces expensive third-party SaaS bills ($3,500+/mo Agora/Twilio fees), check out the Flutter Mediasoup SFU Real-Time Kit:

• ✅ Production Mediasoup SFU Node.js/TypeScript Cluster: Sub-180ms latency, multi-core worker scaling.
• ✅ Complete Flutter Client SDK: Audio/Video call state management, camera switching, audio route routing.
• ✅ Dynamic Simulcast & SVC: Multi-bitrate streaming with automatic network degradation handling.
• ✅ Integrated DRM Overlay: Pre-wired forensic canvas watermark overlay with live user tracing.
• ✅ One-Click Docker Compose: Deploy anywhere (Fly.io, AWS EC2, DigitalOcean, Hetzner).

👉 🇰🇭 Instant Checkout via Telegram (ABA KHQR - $249)
👉 💳 International Card Checkout on Gumroad

Features #

• 🎨 Hardware-Accelerated Canvas: CustomPainter rendered directly via Skia / Impeller on the GPU for silky 60/120 FPS video rendering.
• ⏱️ Dynamic UTC Timestamp Ticking: Second-by-second auto-refreshing UTC timestamp traces the exact second a confidential leak or recording occurred.
• 🛡️ Zero Touch Obstruction: Overlay is wrapped with IgnorePointer and separated with RepaintBoundary to prevent touch event interception and avoid repainting underlying video frames.
• 📐 Circumscribed Radial Coverage: Uses trigonometric circumscribed circle math to guarantee complete corner-to-corner coverage at any rotation angle (-20°, -45°, etc.) across mobile, foldables, and desktop monitors.
• ⚙️ Configurable Forensic Metadata: Authenticated user ID, client IP address, session token, opacity, custom monospace typography, and custom text builders.
• 🚀 Zero Third-Party Dependencies: Pure Flutter framework SDK. Zero dependency bloat, zero native binary conflicts, zero version lock-in.
• 🌐 100% Cross-Platform: iOS, Android, Web, macOS, Windows, and Linux.

Installation #

Add flutter_canvas_watermark to your pubspec.yaml:

dependencies:
  flutter_canvas_watermark: ^1.0.0

Or install via terminal:

flutter pub add flutter_canvas_watermark

Quick Start #

1. Basic Watermark Overlay #

Wrap your video player, PDF viewer, or confidential dashboard in DrmWatermarkOverlay:

import 'package:flutter/material.dart';
import 'package:flutter_canvas_watermark/flutter_canvas_watermark.dart';

class SecureVideoPlayerView extends StatelessWidget {
  const SecureVideoPlayerView({super.key});

  @override
  Widget build(BuildContext context) {
    return DrmWatermarkOverlay(
      config: const DrmWatermarkConfig(
        userId: 'usr_904812',
        clientIp: '203.189.145.22',
        opacity: 0.18,
        angle: -0.35, // ~ -20 degrees
      ),
      child: Center(
        child: Text('Underlying Video or Document Content'),
      ),
    );
  }
}

2. Custom Forensic Text Builder #

Format your watermark text with custom delimiters, timestamps, or confidentiality notices:

final customConfig = DrmWatermarkConfig(
  userId: 'employee@company.internal',
  clientIp: '10.240.0.15',
  textBuilder: (config, timestamp) {
    final utc = timestamp.toUtc();
    return 'CONFIDENTIAL // ${config.userId} // ${utc.hour}:${utc.minute}:${utc.second}';
  },
  opacity: 0.22,
  textStyle: const TextStyle(
    color: Colors.redAccent,
    fontSize: 11,
    fontWeight: FontWeight.bold,
    letterSpacing: 1.5,
  ),
);

3. Standalone Grid Painting #

If you want to render the watermark directly within a custom canvas or Stack without wrapping a child widget:

Stack(
  children: [
    YourCustomVideoWidget(),
    Positioned.fill(
      child: DrmWatermarkGrid(
        config: config,
      ),
    ),
  ],
)

Performance Considerations #

1. Repaint Isolation: DrmWatermarkOverlay wraps the watermark canvas in a RepaintBoundary. Underlying video frames (e.g., Mediasoup, Agora, WebRTC) paint independently without forcing the watermark to recalculate layout.
2. Minimal Timer Overhead: The dynamic timestamp updates via an efficient periodic timer rather than per-frame ticking, reducing CPU utilization by 98% compared to standard animation controllers.
3. Static Mode: Pass updateInterval: Duration.zero if your forensic security policy only requires static identifiers (User ID + Session ID) without second-level timestamps.

Contributing #

Contributions, bug reports, and feature suggestions are welcome! Please feel free to open an issue or submit a pull request on GitHub.

License #

This package is released under the MIT License.