Question

当前我有以下代码：

HeartBeatChanger

这不起作用，因为按照文档的“ picture.toImage（100，100）”不会返回渲染的图像。如何从图片中获取渲染的图像？

编辑：

建议的代码确实起作用，但是，一旦我从互联网上加载SVG，它就不再起作用。

Future<Color> colorFromSvgString(String svgAsString) async {
  final DrawableRoot svgRoot =
      await svg.fromSvgString(svgAsString, svgAsString);
  final picture = svgRoot.toPicture();
  final image = await picture.toImage(100, 100);
  final palette = await PaletteGenerator.fromImage(image);
  return palette.dominantColor.color;
}

Answer 1

我已经对您的代码段进行了测试，可与演示android.svg一起正常使用
您可以看到此演示android.svg的颜色90c020测试结果
您的SVG字符串可能不正确。
您可以在用户界面中显示它，以确保svg字符串正确。

SvgPicture.string(rawSvg)

从网址svg

编辑完整测试代码

import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter_svg/avd.dart';
import 'package:palette_generator/palette_generator.dart';
import 'package:http/http.dart' as http;

void main() => runApp(MyApp());

final String rawSvg = '''<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 96 105">
  <g fill="#97C024" stroke="#97C024" stroke-linejoin="round" stroke-linecap="round">
    <path d="M14,40v24M81,40v24M38,68v24M57,68v24M28,42v31h39v-31z" stroke-width="12"/>
    <path d="M32,5l5,10M64,5l-6,10 " stroke-width="2"/>
  </g>
  <path d="M22,35h51v10h-51zM22,33c0-31,51-31,51,0" fill="#97C024"/>
  <g fill="#FFF">
    <circle cx="36" cy="22" r="2"/>
    <circle cx="59" cy="22" r="2"/>
  </g>
</svg>''';

//var image;

Future<Color> colorFromSvgString(String svgAsString) async {
  final DrawableRoot svgRoot =
  await svg.fromSvgString(svgAsString, svgAsString);
  final picture = svgRoot.toPicture();
  final image = await picture.toImage(100, 100);
  final palette = await PaletteGenerator.fromImage(image);
  return palette.dominantColor.color;
}

Future<Color> colorFromSvgUrl(String svgUrl) async {
  try {
    final response = await http.get(svgUrl);
    print("${response.body}");
    return colorFromSvgString(response.body);
  } catch (e) {
    return null;
  }
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
      //var color = colorFromSvgString(rawSvg);
      var color = colorFromSvgUrl("http://test.com/Android/android.svg");
      print(color.toString());
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            SvgPicture.string(rawSvg),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

调试图像

如何从Flutter中的ui.Picture获取ui.Image？

1 个答案: