如何在flutter中添加png图像，而我们正在创建pdf？

dependencies:
  pdf: ^2.0.0
  flutter_pdfview: ^1.0.0

import 'package:pdf/widgets.dart' as pw;
import 'package:flutter_pdfview/flutter_pdfview.dart';

final pdf = pw.Document();
final imageProvider = pw.MemoryImage(File('path_to_image.png').readAsBytesSync());

pdf.addPage(
  pw.Page(
    build: (pw.Context context) {
      return pw.Image(imageProvider);
    },
  ),
);

final output = File('path_to_output.pdf');
await output.writeAsBytes(await pdf.save());

// 显示PDF
Navigator.push(
  context,
  MaterialPageRoute(
    builder: (context) => PDFView(filePath: output.path),
  ),
);