如何将签名转换为图像，然后将其保存在本地数据库或flutter中的特定URL中？

问题描述

我正在尝试从用户那里收集签名并将其保存到图像中。我已经做得足够远，可以在屏幕上绘画了，但是现在我想单击一个按钮以保存到图像并存储在数据库中。

解决方法

在扑打中，您可以使用签名板：

• 将以下依赖项添加到pubspec.yaml文件中：flutter_signature_pad: ^2.0.2

供参考，请点击signature pad链接。

import 'dart:convert';
import 'dart:math';
import 'dart:typed_data';
import 'dart:ui' as ui;

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_signature_pad/flutter_signature_pad.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await SystemChrome.setPreferredOrientations([DeviceOrientation.landscapeLeft]);
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',theme: ThemeData(
        primarySwatch: Colors.blue,),home: MyHomePage(),);
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _WatermarkPaint extends CustomPainter {
  final String price;
  final String watermark;

  _WatermarkPaint(this.price,this.watermark);

  @override
  void paint(ui.Canvas canvas,ui.Size size) {
    canvas.drawCircle(Offset(size.width / 2,size.height / 2),10.8,Paint()..color = Colors.blue);
  }

  @override
  bool shouldRepaint(_WatermarkPaint oldDelegate) {
    return oldDelegate != this;
  }

  @override
  bool operator ==(Object other) =>
      identical(this,other) || other is _WatermarkPaint && runtimeType == other.runtimeType && price == other.price && watermark == other.watermark;

  @override
  int get hashCode => price.hashCode ^ watermark.hashCode;
}

class _MyHomePageState extends State<MyHomePage> {
  ByteData _img = ByteData(0);
  var color = Colors.red;
  var strokeWidth = 5.0;
  final _sign = GlobalKey<SignatureState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Expanded(
            child: Container(
              child: Padding(
                padding: const EdgeInsets.all(8.0),child: Signature(
                  color: color,key: _sign,onSign: () {
                    final sign = _sign.currentState;
                    debugPrint('${sign.points.length} points in the signature');
                  },backgroundPainter: _WatermarkPaint("2.0","2.0"),strokeWidth: strokeWidth,color: Colors.black12,_img.buffer.lengthInBytes == 0 ? Container() : LimitedBox(maxHeight: 200.0,child: Image.memory(_img.buffer.asUint8List())),Column(
            children: <Widget>[
              Row(
                mainAxisAlignment: MainAxisAlignment.center,children: [
                  MaterialButton(
                      color: Colors.green,onPressed: () async {
                        final sign = _sign.currentState;
                        //retrieve image data,do whatever you want with it (send to server,save locally...)
                        final image = await sign.getData();
                        var data = await image.toByteData(format: ui.ImageByteFormat.png);
                        sign.clear();
                        final encoded = base64.encode(data.buffer.asUint8List());
                        setState(() {
                          _img = data;
                        });
                        debugPrint("onPressed " + encoded);
                      },child: Text("Save")),MaterialButton(
                      color: Colors.grey,onPressed: () {
                        final sign = _sign.currentState;
                        sign.clear();
                        setState(() {
                          _img = ByteData(0);
                        });
                        debugPrint("cleared");
                      },child: Text("Clear")),],Row(
                mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
                  MaterialButton(
                      onPressed: () {
                        setState(() {
                          color = color == Colors.green ? Colors.red : Colors.green;
                        });
                        debugPrint("change color");
                      },child: Text("Change color")),MaterialButton(
                      onPressed: () {
                        setState(() {
                          int min = 1;
                          int max = 10;
                          int selection = min + (Random().nextInt(max - min));
                          strokeWidth = selection.roundToDouble();
                          debugPrint("change stroke width to $selection");
                        });
                      },child: Text("Change stroke width")),)
        ],);
  }
}