How to convert BASE64 string into Image with Flutter?

Question

I'm converting images saved in my Firebase database to Base64 and would like to decode and encode. I've researched similar questions, but am still getting errors. Here is what I have so far?

var image1 = String;

var pic = event.snapshot.value['image'];
var photo = BASE64.decode(pic);
image1 = photo;

I'm getting the following error...

A value of type "List<int>" cannot be assigned to a variable of type "Type"

If you could please provide a reverse process for encoding an image into Base64 so they may be saved back to Firebase, that would be appreciated.

*** UPDATE

Here is my updated code that's still throwing an error.

image1 = event.snapshot.value['image'];
var image = BASE64.decode(image1.toString());
new Image.memory(image),

The error is...

FormatException: Invalid Length must be a multiple of 4

Answer 1

You can convert a Uint8List to a Flutter Image widget using the Image.memory constructor. (Use the Uint8List.fromList constructor to convert a List to Uint8List if necessary.) You can use BASE64.encode to go the other way.

Here's some sample code.

import 'dart:async';
import 'dart:convert';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      theme: new ThemeData.dark(),
      home: new MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  State createState() => new MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> {
  String _base64;

  @override
  void initState() {
    super.initState();
    (() async {
      http.Response response = await http.get(
        'https://flutter.io/images/flutter-mark-square-100.png',
      );
      if (mounted) {
        setState(() {
          _base64 = BASE64.encode(response.bodyBytes);
        });
      }
    })();
  }

  @override
  Widget build(BuildContext context) {
    if (_base64 == null)
      return new Container();
    Uint8List bytes = BASE64.decode(_base64);
    return new Scaffold(
      appBar: new AppBar(title: new Text('Example App')),
      body: new ListTile(
        leading: new Image.memory(bytes),
        title: new Text(_base64),
      ),
    );
  }
}

However, it's generally a bad idea to store large blobs of binary data in your database. It's not playing to the strengths of Firebase realtime database and you will end up wasting bandwidth transmitting data you don't need as well as unnecessary encoding and decoding. You should use the firebase_storage plugin instead, storing the path or download URL of the image in the database.