Flutter 颤振-调整网络图像大小_Flutter_Pdf_Dart

Flutter 颤振-调整网络图像大小

flutter pdf dart

Flutter 颤振-调整网络图像大小,flutter,pdf,dart,Flutter,Pdf,Dart,有没有一种方法可以在不将图像写入存储器的情况下调整图像的大小？我使用的是一个pdf库，图像需要它的字节我所做的是使用http.get获取图像，然后获取将其放入pdf中的字节。问题是我需要在将图像放入pdf之前调整其大小我唯一拥有的是图像的url或UInt8列表 Response response = await http.get(imageUrl); Uint8List imgBytes = response.bodyBytes; 后来： Image( PdfImage.fil

有没有一种方法可以在不将图像写入存储器的情况下调整图像的大小？我使用的是一个pdf库，图像需要它的字节

我所做的是使用http.get获取图像，然后获取将其放入pdf中的字节。问题是我需要在将图像放入pdf之前调整其大小

我唯一拥有的是图像的url或UInt8列表

Response response = await http.get(imageUrl);
Uint8List imgBytes = response.bodyBytes;

后来：

Image(
    PdfImage.file(pdf.document,
    bytes: imageBytes)
),

我使用的Pdf库：

您可以复制下面的粘贴运行完整代码您可以使用ui.instantiateImageCodec并指定targetSight和targetWidth 调整大小后，可以看到输出图像大小变小

代码片段

    String imageUrl = 'https://picsum.photos/250?image=9';
    http.Response response = await http.get(imageUrl);
    originalUnit8List = response.bodyBytes;

    ui.Image originalUiImage = await decodeImageFromList(originalUnit8List);
    ByteData originalByteData = await originalUiImage.toByteData();
    print('original image ByteData size is ${originalByteData.lengthInBytes}');

    var codec = await ui.instantiateImageCodec(originalUnit8List,
        targetHeight: 50, targetWidth: 50);
    var frameInfo = await codec.getNextFrame();
    ui.Image targetUiImage = frameInfo.image;

    ByteData targetByteData =
        await targetUiImage.toByteData(format: ui.ImageByteFormat.png);
    print('target image ByteData size is ${targetByteData.lengthInBytes}');
    targetlUinit8List = targetByteData.buffer.asUint8List();

工作演示的输出

I/flutter (17023): original image ByteData size is 250000
I/flutter (17023): target image ByteData size is 4060

工作演示

I/flutter (17023): original image ByteData size is 250000
I/flutter (17023): target image ByteData size is 4060

完整代码

import 'dart:typed_data';
import 'dart:ui' as ui;
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:io';

void main() {
  runApp(MyApp());
}

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

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  Uint8List targetlUinit8List;
  Uint8List originalUnit8List;

  void _resizeImage() async {
    String imageUrl = 'https://picsum.photos/250?image=9';
    http.Response response = await http.get(imageUrl);
    originalUnit8List = response.bodyBytes;

    ui.Image originalUiImage = await decodeImageFromList(originalUnit8List);
    ByteData originalByteData = await originalUiImage.toByteData();
    print('original image ByteData size is ${originalByteData.lengthInBytes}');

    var codec = await ui.instantiateImageCodec(originalUnit8List,
        targetHeight: 50, targetWidth: 50);
    var frameInfo = await codec.getNextFrame();
    ui.Image targetUiImage = frameInfo.image;

    ByteData targetByteData =
        await targetUiImage.toByteData(format: ui.ImageByteFormat.png);
    print('target image ByteData size is ${targetByteData.lengthInBytes}');
    targetlUinit8List = targetByteData.buffer.asUint8List();

    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            originalUnit8List == null
                ? Container()
                : Image.memory(originalUnit8List),
            targetlUinit8List == null
                ? Container()
                : Image.memory(targetlUinit8List),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _resizeImage,
        tooltip: 'Resize',
        child: Icon(Icons.add),
      ),
    );
  }
}

您可以复制粘贴运行下面的完整代码您可以使用ui.instantiateImageCodec并指定targetSight和targetWidth 调整大小后，可以看到输出图像大小变小

代码片段

    String imageUrl = 'https://picsum.photos/250?image=9';
    http.Response response = await http.get(imageUrl);
    originalUnit8List = response.bodyBytes;

    ui.Image originalUiImage = await decodeImageFromList(originalUnit8List);
    ByteData originalByteData = await originalUiImage.toByteData();
    print('original image ByteData size is ${originalByteData.lengthInBytes}');

    var codec = await ui.instantiateImageCodec(originalUnit8List,
        targetHeight: 50, targetWidth: 50);
    var frameInfo = await codec.getNextFrame();
    ui.Image targetUiImage = frameInfo.image;

    ByteData targetByteData =
        await targetUiImage.toByteData(format: ui.ImageByteFormat.png);
    print('target image ByteData size is ${targetByteData.lengthInBytes}');
    targetlUinit8List = targetByteData.buffer.asUint8List();

工作演示的输出

I/flutter (17023): original image ByteData size is 250000
I/flutter (17023): target image ByteData size is 4060

工作演示

I/flutter (17023): original image ByteData size is 250000
I/flutter (17023): target image ByteData size is 4060

完整代码

import 'dart:typed_data';
import 'dart:ui' as ui;
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:io';

void main() {
  runApp(MyApp());
}

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

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  Uint8List targetlUinit8List;
  Uint8List originalUnit8List;

  void _resizeImage() async {
    String imageUrl = 'https://picsum.photos/250?image=9';
    http.Response response = await http.get(imageUrl);
    originalUnit8List = response.bodyBytes;

    ui.Image originalUiImage = await decodeImageFromList(originalUnit8List);
    ByteData originalByteData = await originalUiImage.toByteData();
    print('original image ByteData size is ${originalByteData.lengthInBytes}');

    var codec = await ui.instantiateImageCodec(originalUnit8List,
        targetHeight: 50, targetWidth: 50);
    var frameInfo = await codec.getNextFrame();
    ui.Image targetUiImage = frameInfo.image;

    ByteData targetByteData =
        await targetUiImage.toByteData(format: ui.ImageByteFormat.png);
    print('target image ByteData size is ${targetByteData.lengthInBytes}');
    targetlUinit8List = targetByteData.buffer.asUint8List();

    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            originalUnit8List == null
                ? Container()
                : Image.memory(originalUnit8List),
            targetlUinit8List == null
                ? Container()
                : Image.memory(targetlUinit8List),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _resizeImage,
        tooltip: 'Resize',
        child: Icon(Icons.add),
      ),
    );
  }
}