problem.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';
import 'dart:io';
import 'dart:typed_data';
import 'dart:ui' as ui;

import 'package:flutter/material.dart';

const double z = 1000000000; // 1e9

void main() async {
      final ui.PictureRecorder recorder = ui.PictureRecorder();
      final Canvas canvas = Canvas(recorder);
      canvas.drawCircle(const Offset(12.0, 12.0), 10.0, Paint()..color = const Color(0xFFFF0000)); // should be obscured
      canvas.drawRect(const Rect.fromLTRB(-z, -z, z/7, z/3), Paint()..color = const Color(0xFF009900)); // should cover everything
      final ui.Picture picture = recorder.endRecording();
      var bytes = await picture.toImageSync(100, 100).  toByteData(format: ui.ImageByteFormat.png);

  // runApp(MaterialApp(
  //   home: Scaffold(
  //     body: Center(
  //       child: CustomPaint(painter: FooPainter(), size: Size(500, 500))
  //     )
  //   )
  // ));

  runApp(MaterialApp(
    home: Scaffold(
      body: Center(
        child: Image.memory(bytes!.buffer.asUint8List()),
      )
    )
  ));
}

// class FooPainter extends CustomPainter {
//   @override
//   void paint(ui.Canvas canvas, ui.Size size) {
//     final ui.Image image;
//     {
//       final ui.PictureRecorder recorder = ui.PictureRecorder();
//       final Canvas canvas = Canvas(recorder);
//       canvas.drawCircle(const Offset(12.0, 12.0), 10.0, Paint()..color = const Color(0xFFFF0000)); // should be obscured
//       canvas.drawRect(const Rect.fromLTRB(-z, -z, z/7, z/3), Paint()..color = const Color(0xFF009900)); // should cover everything
//       final ui.Picture picture = recorder.endRecording();
//       image = picture.toImageSync(100, 100);
//     }
//     canvas.drawImage(image, Offset.zero, Paint());
//   }

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