Flutter -如何在自定义绘图器中缩放和绘制图像？

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

class CustomImagePainter extends CustomPainter {
  ui.Image image;

  CustomImagePainter(this.image);

  @override
  void paint(Canvas canvas, Size size) {
    // 绘制图像
    if (image != null) {
      canvas.drawImageRect(
          image,
          Rect.fromLTRB(0, 0, image.width.toDouble(), image.height.toDouble()),
          Rect.fromLTRB(0, 0, size.width, size.height),
          Paint());
    }
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}

class ImageZoomPage extends StatefulWidget {
  @override
  _ImageZoomPageState createState() => _ImageZoomPageState();
}

class _ImageZoomPageState extends State<ImageZoomPage> {
  double _scale = 1.0;
  double _previousScale = 1.0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Image Zoom'),
      ),
      body: GestureDetector(
        onScaleStart: (ScaleStartDetails details) {
          _previousScale = _scale;
          setState(() {});
        },
        onScaleUpdate: (ScaleUpdateDetails details) {
          setState(() {
            _scale = _previousScale * details.scale;
          });
        },
        onScaleEnd: (ScaleEndDetails details) {
          _previousScale = 1.0;
          setState(() {});
        },
        child: CustomPaint(
          painter: CustomImagePainter(image), // 自定义绘图器
          size: Size.infinite,
        ),
      ),
    );
  }
}

void main() async {
  // 加载图像
  final ByteData data = await rootBundle.load('assets/image.jpg');
  ui.Image image = await decodeImageFromList(data.buffer.asUint8List());
  
  runApp(MaterialApp(
    home: ImageZoomPage(),
  ));
}