Future<Uint8List> to Base64 or PNG in Flutter

Question

I need to convert a Future<Uint8List> to Base64 or PNG in Flutter, I am using this pub to get signature and export it but when I call toPngBytes() method (method in pub) it returns a Future<Uint8List> and I need to convert it to Base64 format or List<int> at least ByteData format, I can not convert it to a more usable format for me, can anyone help me to resolve this.

_controller.toPngBytes(); // _controller is a variable that holds info about my signature.

Solution 1

import 'dart:convert';

// async variant
final imageData = await _controller.toPngBytes(); // must be called in async method
final imageEncoded = base64.encode(imageData); // returns base64 string

// callback variant
_controller.toPngBytes().then((data) {
 final imageEncoded = base64.encode(data); 
});

Solution 2

This function made me upload an image to Xano correctly:

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

String uint8ListTob64(Uint8List uint8list) {
  String base64String = base64Encode(uint8list);
  String header = "data:image/png;base64,";
  return header + base64String;
}

You can transform an image into Uint8List in the following way:

String path = "image.png";
File file = File(path);
Uint8List uint8list = file.readAsBytesSync();
//or
Uint8List uint8list = await file.readAsBytes();

Comments

[pskink]

what is wrong with Uint8List?

[SerNet OE]

Basicly not usefull in my case

[pskink]

and ByteData is more useful? if so, use ByteData.sublistView constructor

[SerNet OE]

Actually List<int> is a lot more useful for me to use base64Encode(), I am not familiar with ` ByteData.sublistView` can you give an example for my case please?

[pskink]

"Actually List<int> is a lot more useful for me " - Uint8List is a List<int> - see Implemented types it the link i posted

[SerNet OE]

Of courese I tried it but it is not appliciable because toPngBytes() returns Future<Uint8List> but base64Encode() takes paremeter type List<int>

[BambinoUA]

Did you read the comments? Do you know what is async/await? Update answer.

[SerNet OE]

Yes, I read them but I did not understand why I should call it in async method but now, I understand it thanks for helping, now I know how to use Future variables.

[saddam]

how to convert Uint8List to Image dataType.