如何在 flutter 中将图像文件转换为 base64 字符串？

Question

我正在尝试在 flutter 中转换图像文件：

 File _img=new File('/data/user/0/com.example.test3/app_flutter/2020-10-29T17:18:56.210347.png');
 List<int> imageBytes = _img.readAsBytesSync();
 String imageB64 = base64Encode(imageBytes);
 print(imageB64);

但它看起来像是一个错误的 base64 字符串，我无法在转换网站上解码为图像： https://codebeautify.org/base64-to-image-converter

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

dart base64 格式与其他格式不同吗？谢谢

Answer 1

您必须将字节转换为 Uint8List 对象而不是 List<int>:

File _img = File(
   '/data/user/0/com.example.test3/app_flutter/2020-10-29T17:18:56.210347.png');
final bytes = Uint8List.fromList(_img.readAsBytesSync());
final imgBase64 = base64Encode(bytes);
print(imgBase64);

Answer 2

我发现'print'函数的这种情况无法显示完整的base64代码。如果要验证，需要导出到文本文件：

 _write(String text) async {
    final File file = File('/storage/emulated/0/xxx/my_file.txt');
    await file.writeAsString(text);
    print(file);
  }

如何在 flutter 中将图像文件转换为 base64 字符串？

How to convert image file to base64 String in flutter?

base64

file

dart

flutter