image_guard 0.1.0-dev.2

On-device NSFW (18+) image detection and compression to an exact byte limit and resolution, powered by a Rust core.

example/lib/main.dart

import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:image_guard/image_guard.dart';
import 'package:image_picker/image_picker.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  // Load the native library + NSFW model once at startup.
  await SafeImage.initialize();
  runApp(const MaterialApp(home: DemoPage()));
}

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

  @override
  State<DemoPage> createState() => _DemoPageState();
}

class _DemoPageState extends State<DemoPage> {
  final _kb = TextEditingController(text: '50');
  final _maxWidth = TextEditingController(text: '1080');
  final _maxHeight = TextEditingController(text: '1080');
  SafeImageFormat _format = SafeImageFormat.jpeg;
  bool _keepOriginal = true;

  XFile? _picked;
  Uint8List? _original;
  SafeImageProcessResult? _result;
  String? _error;
  bool _busy = false;

  int? _parse(TextEditingController c) =>
      c.text.trim().isEmpty ? null : int.tryParse(c.text.trim());

  Future<void> _pick(ImageSource source) async {
    // imageQuality makes iOS return JPEG instead of HEIC (not supported yet).
    final file = await ImagePicker().pickImage(
      source: source,
      imageQuality: 100,
    );
    if (file == null) return;
    _picked = file;
    _original = await file.readAsBytes();
    await _run();
  }

  Future<void> _run() async {
    final file = _picked;
    if (file == null) return;
    setState(() {
      _busy = true;
      _error = null;
      _result = null;
    });
    try {
      final options = SafeImageOptions(
        maxBytes: (_parse(_kb) ?? 0) * 1024,
        maxWidth: _parse(_maxWidth),
        maxHeight: _parse(_maxHeight),
        format: _format,
        keepOriginalIfFits: _keepOriginal,
      );
      final r = await SafeImage.process(
        SafeImageSource.file(file.path),
        options: options,
      );
      setState(() => _result = r);
    } on SafeImageException catch (e) {
      setState(() => _error = '${e.code.name}: ${e.message}');
    } finally {
      setState(() => _busy = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final r = _result;
    return Scaffold(
      appBar: AppBar(title: const Text('image_guard demo')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          Row(
            children: [
              Expanded(child: _field(_kb, 'Max size (KB)')),
              const SizedBox(width: 8),
              Expanded(child: _field(_maxWidth, 'Max width')),
              const SizedBox(width: 8),
              Expanded(child: _field(_maxHeight, 'Max height')),
            ],
          ),
          const SizedBox(height: 8),
          Wrap(
            spacing: 8,
            crossAxisAlignment: WrapCrossAlignment.center,
            children: [
              SegmentedButton<SafeImageFormat>(
                segments: const [
                  ButtonSegment(
                    value: SafeImageFormat.jpeg,
                    label: Text('JPEG'),
                  ),
                  ButtonSegment(value: SafeImageFormat.png, label: Text('PNG')),
                ],
                selected: {_format},
                onSelectionChanged: (s) => setState(() => _format = s.first),
              ),
              FilterChip(
                label: const Text('Keep original if it fits'),
                selected: _keepOriginal,
                onSelected: (v) => setState(() => _keepOriginal = v),
              ),
            ],
          ),
          const SizedBox(height: 8),
          Wrap(
            spacing: 8,
            children: [
              FilledButton.icon(
                onPressed: _busy ? null : () => _pick(ImageSource.gallery),
                icon: const Icon(Icons.photo),
                label: const Text('Gallery'),
              ),
              FilledButton.tonalIcon(
                onPressed: _busy ? null : () => _pick(ImageSource.camera),
                icon: const Icon(Icons.camera_alt),
                label: const Text('Camera'),
              ),
              OutlinedButton(
                onPressed: _busy || _picked == null ? null : _run,
                child: const Text('Apply again'),
              ),
            ],
          ),
          const SizedBox(height: 16),
          if (_busy) const LinearProgressIndicator(),
          if (_error != null)
            Text(
              _error!,
              style: TextStyle(color: Theme.of(context).colorScheme.error),
            ),
          if (r != null) ...[
            _VerdictCard(report: r.safety),
            const SizedBox(height: 12),
            if (r.image case final img?) ...[
              Text(
                'Before: ${img.originalWidth}×${img.originalHeight} '
                '${img.originalFormat.name}, ${(img.originalSizeBytes / 1024).toStringAsFixed(1)} KB\n'
                'After:  ${img.width}×${img.height} ${img.format.name}, '
                '${img.sizeKb.toStringAsFixed(1)} KB'
                '${img.quality != null ? ', quality ${img.quality}' : ''}\n'
                '${img.keptOriginal ? 'Original kept (already fits)' : '${img.attempts} encode attempts'}'
                ' · ${img.elapsed.inMilliseconds} ms',
              ),
              const SizedBox(height: 12),
              Row(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  if (_original != null)
                    Expanded(child: _preview('Original', _original!)),
                  const SizedBox(width: 8),
                  Expanded(child: _preview('Result', img.bytes)),
                ],
              ),
            ] else
              const Text('Rejected: the image was not compressed or shown.'),
          ],
        ],
      ),
    );
  }

  Widget _field(TextEditingController c, String label) => TextField(
    controller: c,
    keyboardType: TextInputType.number,
    decoration: InputDecoration(
      labelText: label,
      border: const OutlineInputBorder(),
    ),
  );

  Widget _preview(String title, Uint8List bytes) => Column(
    crossAxisAlignment: CrossAxisAlignment.start,
    children: [
      Text(title),
      Image.memory(bytes, fit: BoxFit.contain),
    ],
  );
}

class _VerdictCard extends StatelessWidget {
  const _VerdictCard({required this.report});

  final SafetyReport report;

  @override
  Widget build(BuildContext context) {
    final (color, label) = switch (report.verdict) {
      Verdict.safe => (Colors.green, 'SAFE – can be uploaded'),
      Verdict.uncertain => (Colors.orange, 'UNCERTAIN – needs review'),
      Verdict.unsafe => (Colors.red, '18+ / UNSAFE – rejected'),
    };
    return Card(
      color: color.withValues(alpha: 0.12),
      child: Padding(
        padding: const EdgeInsets.all(12),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              label,
              style: TextStyle(color: color, fontWeight: FontWeight.bold),
            ),
            Text(
              'NSFW score ${(report.nsfwScore * 100).toStringAsFixed(1)} % '
              '· ${report.elapsed.inMilliseconds} ms',
            ),
            const SizedBox(height: 8),
            for (final e in report.scores.toMap().entries)
              Row(
                children: [
                  SizedBox(width: 72, child: Text(e.key)),
                  Expanded(child: LinearProgressIndicator(value: e.value)),
                  SizedBox(
                    width: 56,
                    child: Text(
                      '${(e.value * 100).toStringAsFixed(1)}%',
                      textAlign: TextAlign.right,
                    ),
                  ),
                ],
              ),
          ],
        ),
      ),
    );
  }
}