Created
June 29, 2018 08:39
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Signature to image transformation
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import 'dart:typed_data'; | |
import 'package:flutter/material.dart'; | |
import 'dart:ui' as ui; | |
void main() => runApp(new MaterialApp( | |
home: new HomePage(), | |
debugShowCheckedModeBanner: false, | |
)); | |
class HomePage extends StatefulWidget { | |
@override | |
HomePageState createState() => new HomePageState(); | |
} | |
class HomePageState extends State<HomePage> { | |
List<Offset> _points = <Offset>[]; | |
ByteData imgBytes= new ByteData(1024); | |
void saveToImage(List<Offset> points) async { | |
final recorder = new ui.PictureRecorder(); | |
final canvas = new Canvas(recorder, | |
new Rect.fromPoints(new Offset(0.0, 0.0), new Offset(200.0, 200.0))); | |
Paint paint = new Paint() | |
..color = Colors.black | |
..strokeCap = StrokeCap.round | |
..strokeWidth = 5.0; | |
for (int i = 0; i < points.length - 1; i++) { | |
if (points[i] != null && points[i + 1] != null) { | |
canvas.drawLine(points[i], points[i + 1], paint); | |
} | |
} | |
final picture = recorder.endRecording(); | |
final img = picture.toImage(200, 200); | |
final pngBytes = await img.toByteData(format: ui.ImageByteFormat.png); | |
setState(() { | |
imgBytes = pngBytes; | |
}); | |
} | |
@override | |
Widget build(BuildContext context) { | |
return new Scaffold( | |
body: new Column( | |
crossAxisAlignment: CrossAxisAlignment.center, | |
mainAxisAlignment: MainAxisAlignment.spaceBetween, | |
children: <Widget>[ | |
new Container( | |
child: new GestureDetector( | |
onPanUpdate: (DragUpdateDetails details) { | |
setState(() { | |
RenderBox object = context.findRenderObject(); | |
Offset _localPosition = | |
object.globalToLocal(details.globalPosition); | |
_points = new List.from(_points)..add(_localPosition); | |
}); | |
}, | |
onPanEnd: (DragEndDetails details) => _points.add(null), | |
child: new CustomPaint( | |
painter: new Signature(points: _points), | |
size: new Size(200.0, 200.0), | |
), | |
), | |
), | |
new Image.memory(new Uint8List.view(imgBytes.buffer)), | |
], | |
), | |
floatingActionButton: new FloatingActionButton( | |
child: new Icon(Icons.edit), | |
onPressed: () => saveToImage(_points), | |
), | |
); | |
} | |
} | |
class Signature extends CustomPainter { | |
List<Offset> points; //offset is object with x,y | |
Signature({this.points}); | |
@override | |
void paint(Canvas canvas, Size size) { | |
Paint paint = new Paint() | |
..color = Colors.black | |
..strokeCap = StrokeCap.round | |
..strokeWidth = 5.0; | |
for (int i = 0; i < points.length - 1; i++) { | |
if (points[i] != null && points[i + 1] != null) { | |
canvas.drawLine(points[i], points[i + 1], paint); | |
} | |
} | |
} | |
@override | |
bool shouldRepaint(Signature oldDelegate) => oldDelegate.points != points; | |
} |
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