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

Amir.n3t · Accepted Answer · 2019-04-16 03:07:13Z

121

There's a simpler way using 'dart:convert' package

Image.memory(base64Decode(base64String));

Implementation and some useful methods :

import 'dart:convert';
import 'dart:typed_data';
import 'package:flutter/widgets.dart';


Image imageFromBase64String(String base64String) {
  return Image.memory(base64Decode(base64String));
}

Uint8List dataFromBase64String(String base64String) {
  return base64Decode(base64String);
}

String base64String(Uint8List data) {
  return base64Encode(data);
}

answered Apr 16, 2019 at 3:07

Amir.n3t

3,5673 gold badges28 silver badges31 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

kris Over a year ago

The method 'memory' isn't defined for the type 'Image'. Try correcting the name to the name of an existing method, or defining a method named 'memory'.

... I'm finding references to Image.memory when searching on the web, but not of this error, nor of it being deprecated. How do I get the Image.memory method??

Maryam K Over a year ago

@kris Have you imported import 'package:flutter/widgets.dart';

Oded Ben Dov Oct 2 at 5:09

Any idea how to make this async? I get a feeling it's running on the main UI thread (whatever that means in Flutter)

Collin Jackson · Accepted Answer · 2017-09-12 01:29:40Z

57

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.

edited Sep 12, 2017 at 1:29

answered Sep 10, 2017 at 22:08

Collin Jackson

117k31 gold badges229 silver badges154 bronze badges

10 Comments

Charles Jr Over a year ago

Got it. Now its says Uint8ClampedList cannot be assigned to variable Uint8List? Please explain

Charles Jr Over a year ago

When I run this new Image.memory(photo.toList()), My app breaks and I get the following error Format Exception: Invalid Length, must be multiple of 4 Please help

Collin Jackson Over a year ago

Please update your question with the code you're using, because I don't see a call to toList(). It sounds like you're directly calling toList() on a String, which will produce a List of base64 characters. This list isn't a binary representation of the decoded image, so that's probably why you're running into an error when it can't be rendered. Convert the decoded image (the output of decode()) to a Uint8List using new Uint8List.fromList().

Collin Jackson Over a year ago

That said, I would strongly suggest you try firebase_storage, it is a much better approach than storing base64 encoded images in a database.

Charles Jr Over a year ago

Thanks @CollinJackson , The problem is that I currently have an iOS Swift app that I'm updating where I've saved user photos with Base64. There's only a few users but I would like to allow them to access their photos and if they change them then save them and new ones to FirebaseStorage. I've updated the question with my new results.

|

Jeferson Rivera · Accepted Answer · 2019-03-26 04:10:27Z

27

Uint8List _bytesImage;

String _imgString = 'iVBORw0KGgoAAAANSUhEUg.....';

_bytesImage = Base64Decoder().convert(_imgString);

Image.memory(_bytesImage)

answered Mar 26, 2019 at 4:10

Jeferson Rivera

5046 silver badges4 bronze badges

2 Comments

Michael Over a year ago

How do I use this on a CircleAvatar background Image? I have tried several things including backgroundImage: Image.memory(_bytesImage);

Michael Over a year ago

Nevermind, I found that I could just add .image to the end there and it worked: backgroundImage: Image.memory(_bytesImage).image;

luisdemarchi · Accepted Answer · 2019-08-29 20:30:42Z

12

To open a camera photo (temporary folder), editing a file and then turning it into Base64:

Code:

import 'dart:convert';
import 'package:image/image.dart' as ImageProcess;

File file = File(imagePath);
final _imageFile = ImageProcess.decodeImage(
  file.readAsBytesSync(),
);

...edit file...

String base64Image = base64Encode(ImageProcess.encodePng(_imageFile));

Decode and show:

import 'dart:convert';
import 'package:image/image.dart' as ImageProcess;

final _byteImage = Base64Decoder().convert(base64Image);
Widget image = Image.memory(_byteImage)

edited Aug 29, 2019 at 20:30

answered Aug 29, 2019 at 19:17

luisdemarchi

1,57222 silver badges30 bronze badges

Comments

abhijith k · Accepted Answer · 2021-07-29 10:04:33Z

11

import

import 'dart:convert';
import 'dart:typed_data';

from screen load the data and assign to this variable

    Uint8List _bytes;
  _bytes = Base64Decoder().convert("iVBORw0KGgoAAAANSUhEUgAAANgAAA......");

In code tree structure widget

Image.memory(_bytes)

answered Jul 29, 2021 at 10:04

abhijith k

3994 silver badges5 bronze badges

Comments

Pedro Molina · Accepted Answer · 2021-02-24 17:07:22Z

5

With this simple method i could set an image in flutter. The image attribute is the base64 image as string, example:

TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb2

Try the next:

Widget getImagenBase64(String imagen) {
    _imageBase64 = imagen;
    const Base64Codec base64 = Base64Codec();
    if (_imageBase64 == null) return new Container();
    bytes = base64.decode(_imageBase64);
    return Image.memory(
          bytes,
          width: 200,
          fit: BoxFit.fitWidth,
       
    );
  }

I hope this work for you. Happy coding.

answered Feb 24, 2021 at 17:07

Pedro Molina

1,52419 silver badges12 bronze badges

1 Comment

0xPunt Over a year ago

This is a bad practice to create a widget and return it in a function. Create a stateless widget which take your 'String imagen' as attributes and return your Image.memory

ANUSREE P · Accepted Answer · 2023-06-22 08:52:30Z

3

this worked for me

ClipRRect(
                borderRadius: BorderRadius.circular(100),
                child: Image.memory(
                  base64Decode(widget.imgBase64 ?? ''),
                  gaplessPlayback: true,
                  fit: BoxFit.cover,
                )),

answered Jun 22, 2023 at 8:52

ANUSREE P

1411 silver badge2 bronze badges

2 Comments

Sagar Shah Over a year ago

gaplessPlayback: true, helps to load the image

Rezwan Over a year ago

Yes! gaplessPlayback:true did the trick!

user22474798 · Accepted Answer · 2023-08-31 02:44:07Z

2

Supposing we have a DataURL stored in a String of a format similar to the following:

String dataUrl = "data:image/jpeg;base64,/9j/4AAQSk...";

A simple solution exists to render this as an Image via Uri:

Image.memory(
    Uri.parse(dataUrl).data?.contentAsBytes()
    ?? Uint8List(0),
)

This is a null-safe solution, and can be easily modified into the following for older versions of Dart:

Image.memory(Uri.parse(dataUrl).data.contentAsBytes())

answered Aug 31, 2023 at 2:44

user22474798

537 bronze badges

Comments

Hai Dinh · Accepted Answer · 2023-12-22 03:08:02Z

1

 import 'package:path_provider/path_provider.dart';

    final time = DateTime.now().toIso8601String().replaceAll('.', ':');
    final name = 'signature_$time.png';
    
    final String dir = (await getApplicationDocumentsDirectory()).path;
    final File file = File("$dir/$name.png");
    
    // Upload it to server or download to your local.
    await file.writeAsBytes(img_base64!);

Hope it help!

answered Dec 22, 2023 at 3:08

Hai Dinh

1,5212 gold badges20 silver badges32 bronze badges

Comments

Haashir-Shakeel · Accepted Answer · 2023-04-26 21:20:05Z

Do check the type using runtimeType, In my case it was String. My function was returning Future<<U'intList>> i changed it to Future<<s'tring>> and used Image.Memory like this: Image.memory(base64Decode(_imageBytes!)

Here is my full code:

import 'dart:convert';
import 'dart:typed_data';

import 'package:flutter/material.dart';

import 'getResponseFromNodeApi.dart';
import 'getResponseFromStabilityAi.dart';

class MyImageWidget extends StatefulWidget {
  const MyImageWidget({Key? key}) : super(key: key);

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

class _MyImageWidgetState extends State<MyImageWidget> {
  String? _imageBytes;
  String? _errorMessage;

  @override
  void initState() {
    super.initState();

    _generateImage();
  }

  Future<void> _generateImage() async {
    setState(() {
      _imageBytes = null;
      _errorMessage = null;
    });

    try {
      // final bytes = await getResponseFromStabilityAi();
      final bytes = await getResponseFromNodeApi(textPrompt: 'light House');
      // List<int> bytes2 = utf8.encode(bytes as String);
      setState(() {
        _imageBytes = bytes;
      });
    } catch (e) {
      setState(() {
        print(e);
        _errorMessage = 'Failed to generate image: $e';
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Generated Image'),
      ),
      body: Center(
        child: _imageBytes != null
            ? Image.memory(base64Decode(_imageBytes!))
            : _errorMessage != null
            ? Text(_errorMessage!)
            : const CircularProgressIndicator(),
      ),
    );
  }
}

I hope this helps

Collectives™ on Stack Overflow

How to convert BASE64 string into Image with Flutter?

10 Answers 10

3 Comments

10 Comments

2 Comments

Comments

Comments

1 Comment

2 Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

10 Answers 10

3 Comments

10 Comments

2 Comments

Comments

Comments

1 Comment

2 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related