Future to Base64 or PNG in Flutter

Question

I need to convert a Future 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 and I need to convert it to Base64 format or List 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.

user_1798328 · Answer

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); 
});

user_3997782 · Answer

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();

Future<Uint8List> to Base64 or PNG in Flutter

2 Answers