首页
学习
活动
专区
工具
TVP
发布
社区首页 >问答首页 >是否可以使用Dart/Flutter绘制图像?

是否可以使用Dart/Flutter绘制图像?
EN

Stack Overflow用户
提问于 2018-06-02 09:35:28
回答 1查看 10.8K关注 0票数 7

我正在寻找一种从flutter应用程序中生成图像(jpeg或png)的方法。图像将由圆、线、文本等组成。

似乎确实有一种使用画布(https://docs.flutter.io/flutter/dart-ui/Canvas/Canvas.html)绘制到屏幕的方法,但是似乎没有等效的方法来创建可以在应用程序内呈现或在应用程序外发送/使用的图像。

有没有可用于绘制图像的dart库?考虑到底层的skia框架,这似乎是可能的。在Dart-html包中有一个CanvasRenderingContext2D。

编辑:获得下面这样的工作(根据Richard的建议)将是一个开始:

import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'dart:ui';
import 'dart:typed_data';
import 'dart:async';
import 'dart:io';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

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

class _MyHomePageState extends State<MyHomePage> {
  Image _image;

  @override
  void initState() {
    super.initState();
    _image = new Image.network(
      'https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_120x44dp.png',
    );
  }

  Future<String> get _localPath async {
    final directory =
        await getApplicationDocumentsDirectory(); //From path_provider package
    return directory.path;
  }

  Future<File> get _localFile async {
    final path = await _localPath;
    return new File('$path/tempImage.png');
  }

  Future<File> writeImage(ByteData pngBytes) async {
    final file = await _localFile;
    // Write the file
    file.writeAsBytes(pngBytes.buffer.asUint8List());
    return file;
  }

  _generateImage() {
    _generate().then((val) => setState(() {
          _image = val;
        }));
  }

  Future<Image> _generate() async {
    PictureRecorder recorder = new PictureRecorder();
    Canvas c = new Canvas(recorder);
    var rect = new Rect.fromLTWH(0.0, 0.0, 100.0, 100.0);
    c.clipRect(rect);

    final paint = new Paint();
    paint.strokeWidth = 2.0;
    paint.color = const Color(0xFF333333);
    paint.style = PaintingStyle.fill;

    final offset = new Offset(50.0, 50.0);
    c.drawCircle(offset, 40.0, paint);
    var picture = recorder.endRecording();

    final pngBytes =
        await picture.toImage(100, 100).toByteData(format: ImageByteFormat.png);

    //Aim #1. Upade _image with generated image.
    var image = Image.memory(pngBytes.buffer.asUint8List());
    return image;

    //new Image.memory(pngBytes.buffer.asUint8List());
    // _image = new Image.network(
    //   'https://github.com/flutter/website/blob/master/_includes/code/layout/lakes/images/lake.jpg?raw=true',
    // );

    //Aim #2. Write image to file system.
    //writeImage(pngBytes);
    //Make a temporary file (see elsewhere on SO) and writeAsBytes(pngBytes.buffer.asUInt8List())
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            _image,
          ],
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _generateImage,
        tooltip: 'Generate',
        child: new Icon(Icons.add),
      ),
    );
  }
}
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2018-06-02 10:18:19

PictureRecorder允许您创建画布,使用画布绘制方法并提供返回PictureendRecording()。您可以将此图片绘制到其他场景或画布上,或者使用.toImage(width, height).toByteData(format)将其转换为PNG (或者不支持raw - jpeg )。

例如:

import 'dart:ui';
import 'dart:typed_data';
....
  PictureRecorder recorder = new PictureRecorder();
  Canvas c = new Canvas(recorder);
  c.drawPaint(paint); // etc
  Picture p = recorder.endRecording();
  ByteData pngBytes =
      await p.toImage(100, 100).toByteData(format: ImageByteFormat.png);

确保您使用的是flutter 0.4.4,否则可能无法使用format参数。

看过您的编辑后,我怀疑您实际上是在寻找CustomPainter,它为您提供了一个可以在其上绘图的画布。下面是一个类似问题的example

票数 13
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接:

https://stackoverflow.com/questions/50652767

复制
相关文章

相似问题

领券
问题归档专栏文章快讯文章归档关键词归档开发者手册归档开发者手册 Section 归档