just_screenshot

A Flutter plugin for capturing screenshots on Windows desktop. Supports full screen capture and interactive region selection.

Features

• 🖥️ Full Screen Capture: Capture the entire primary display with a single call
• ✂️ Region Selection: Interactive overlay for selecting and capturing specific screen areas
• 🖱️ Cursor Support: Optional cursor inclusion in screenshots
• 🎨 PNG Encoding: Lossless PNG format with automatic encoding
• ⚡ High Performance: Fast native Windows implementation using Win32 APIs
• 🎯 DPI Aware: Correct handling of high-DPI displays (125%, 150%, 200% scaling)

Platform Support

Platform	Support
Windows	✅ Full
macOS	❌ Not yet
Linux	❌ Not yet

Installation

Add this to your package's pubspec.yaml file:

dependencies:
  just_screenshot: ^0.1.0

Then run:

flutter pub get

Usage

Capture Full Screen

import 'package:just_screenshot/screenshot.dart';

// Capture the entire primary display
final CapturedData? data = await Screenshot.instance.capture(
  mode: ScreenshotMode.screen,
  includeCursor: true, // Optional, defaults to false
);

if (data != null) {
  print('Captured ${data.width}x${data.height} screenshot');
  // Use data.bytes (PNG-encoded Uint8List)
  Image.memory(data.bytes);
}

Capture Screen Region

import 'package:screenshot/screenshot.dart';

// Show interactive overlay for region selection
final CapturedData? data = await Screenshot.instance.capture(
  mode: ScreenshotMode.region,
);

if (data != null) {
  print('Captured region: ${data.width}x${data.height}');
  Image.memory(data.bytes);
} else {
  print('User cancelled selection');
}

Error Handling

import 'package:screenshot/screenshot.dart';

try {
  final CapturedData? data = await Screenshot.instance.capture(
    mode: ScreenshotMode.screen,
  );
  
  if (data != null) {
    // Screenshot captured successfully
    Image.memory(data.bytes);
  } else {
    // User cancelled (region mode only)
    print('Capture cancelled');
  }
} on ScreenshotException catch (e) {
  // Handle errors
  switch (e.code) {
    case 'cancelled':
      print('User cancelled: ${e.message}');
      break;
    case 'internal_error':
      print('Internal error: ${e.message}');
      print('Details: ${e.details}');
      break;
    case 'invalid_argument':
      print('Invalid argument: ${e.message}');
      break;
    default:
      print('Error: ${e.message}');
  }
}

API Reference

Screenshot

Singleton class providing screenshot capture functionality.

Methods

• capture({required ScreenshotMode mode, bool includeCursor = false, int? displayId}): Capture a screenshot
  • mode: Capture mode (screen or region)
  • includeCursor: Whether to include the cursor (default: false)
  • displayId: Target display ID (default: null = primary display)
  • Returns: Future<CapturedData?> - Captured screenshot or null if cancelled

ScreenshotMode

Enum defining capture behavior:

• screen: Capture entire primary display
• region: User-selected rectangular area via interactive overlay

CapturedData

Immutable class containing screenshot data:

• width (int): Image width in pixels
• height (int): Image height in pixels
• bytes (Uint8List): PNG-encoded image data

ScreenshotException

Exception thrown when capture fails:

• code (String): Error code (cancelled, internal_error, invalid_argument, not_supported)
• message (String): Human-readable error message
• details (dynamic): Optional additional error details

Region Selection Controls

When using ScreenshotMode.region, an interactive overlay appears:

• Left-click and drag: Select rectangular region
• Release mouse: Confirm selection and capture
• ESC key: Cancel selection
• Right-click: Cancel selection

Requirements

• Flutter 3.3.0 or higher
• Dart 3.7.2 or higher
• Windows 10 or higher

Performance

• Full screen capture: <500ms @ 1920x1080
• Overlay responsiveness: <16ms (60 FPS mouse tracking)
• Memory usage: <100MB per capture

Example

See the example/ directory for a complete demonstration app showing both screen and region capture modes.

cd example
flutter run -d windows

Contributing

Contributions are welcome! Please read the contributing guidelines before submitting pull requests.

License

This project is licensed under the BSD 3-Clause License - see the LICENSE file for details.

Changelog

See CHANGELOG.md for version history.

Issues

Please file issues on the GitHub issue tracker.