abhu66/flutter_captcha

omjo_captcha

pub package

A customizable, client-side CAPTCHA widget for Flutter with randomized colorful characters and noise lines.
No backend required — perfect for login forms, guestbooks, or simple human verification needs.

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Captcha Screenshot

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✨ Features

• 🎨 Randomized colored characters
• 🔀 Noise/disturbance lines for bot resistance
• 🔄 Easy CAPTCHA refresh
• ✅ Custom validation logic
• 🚫 Works entirely offline (no server needed)

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🌐 Live Demo

🧪 Try it directly in your browser (no installation needed):
👉 https://omjocaptcha.netlify.app

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📦 Installation

Add this to your pubspec.yaml:

dependencies:
  omjo_captcha: ^0.0.1

Then run:

flutter pub get

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🚀 Usage

Here's a simple example:

import 'package:flutter/material.dart';
import 'package:omjo_captcha/omjo_captcha.dart';
import 'dart:math';

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

  @override
  State<CaptchaPreview> createState() => _CaptchaPreviewState();
}

class _CaptchaPreviewState extends State<CaptchaPreview> {
  late List<CaptchaChar> characters;
  late List<CaptchaLine> lines;

  @override
  void initState() {
    super.initState();
    _generateCaptcha();
  }

  void _generateCaptcha() {
    final random = Random();
    const text = 'A7B2X';

    characters = text.split('').map((char) {
      return CaptchaChar(
        char: char,
        color: _randomColor(random),
        yOffset: 10 + random.nextDouble() * 10,
        rotation: (random.nextDouble() - 0.5) * 0.3,
      );
    }).toList();

    lines = List.generate(5, (_) {
      return CaptchaLine(
        start: Offset(random.nextDouble() * 120, random.nextDouble() * 50),
        end: Offset(random.nextDouble() * 120, random.nextDouble() * 50),
        color: _randomColor(random),
      );
    });

    setState(() {});
  }

  Color _randomColor(Random random) {
    return Color.fromARGB(
      255,
      100 + random.nextInt(156),
      100 + random.nextInt(156),
      100 + random.nextInt(156),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        CustomPaint(
          size: const Size(150, 50),
          painter: CaptchaPainter(characters, lines),
        ),
        const SizedBox(height: 10),
        ElevatedButton(
          onPressed: _generateCaptcha,
          child: const Text('Refresh Captcha'),
        ),
      ],
    );
  }
}

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📁 Folder Structure

lib/
├── omjo_captcha.dart
└── src/
    ├── captcha_painter.dart
    ├── models/
    │   ├── captcha_char.dart
    │   └── captcha_line.dart

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🧪 Example App

Clone this repo and run the example:

cd example
flutter run

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💡 Tips

• You can wrap this CAPTCHA in a TextFormField widget for login forms.
• Combine with your auth logic to validate user input against captchaText.

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🛠️ Contributing

Contributions are welcome!
If you found a bug or want a new feature, please open an issue or submit a pull request.

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Support the Project

If you find this plugin helpful, consider supporting its development:

• Buy Me a Coffee

Your support is greatly appreciated!

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📄 License

MIT © Abu Khoerul Iskandar Ali (Omjo)
See LICENSE for details.

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🙌 Credits

Built with 💙 using Flutter.