将图像编码为 base64 字符串

Question

我正在尝试使用库 image_picker.. 从 dart 中的照片库上传图像，这工作正常..

然后我尝试将所选图像转换为 bas64 字符串，如下所示：

imageSelectorGallery() async {
    _image = await ImagePicker.pickImage(
      source: ImageSource.gallery,
      // maxHeight: 50.0,
      // maxWidth: 50.0,
    );
    List<int> imageBytes = _image.readAsBytesSync();
    print(imageBytes);
    String base64Image = base64Encode(imageBytes);
    print('string is');
    print(base64Image);
    print("You selected gallery image : " + _image.path);
    setState(() {});
   }

但这总是返回一个不正确的字符串..例如：

_9j_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_-AAEEpGSUYAAQEAAAEAAQAA_9sAQwACAQEBAQECAQEBAgICAgIEAwICAgIFBAQDBAYFBgYGBQYGBgcJCAYHCQcGBggLCAkKCgoKCgYICwwLCgwJCgoK_9sAQwECAgICAgIFAwMFCgcGBwoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoK_8AAEQgFAAPAAwEiAAIRAQMRAf_EAB8AAAEFAQEBAQEBAAAAAAAAAAABAgMEBQYHCAkKC__EALUQAAIBAwMCBAMFBQQEAAABfQECAwAEEQUSITFBBhNRYQcicRQygZGhCCNCscEVUtHwJDNicoIJChYXGBkaJSYnKCkqNDU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ 2hpanN0dXZ3eHl6g4SFhoeIiYq

而且这不能转换成图片..

问题出在哪里以及如何解决？

Answer 1

您只将编码字符串的前 1024 个字符复制到问题中。也许print 命令截断了它。此外，在线工具似乎更喜欢（需要？） URL 安全版本，因此正如 Günter 所说，使用 base64UrlEncode。

要确认您使用的字符串长度大致正确，请添加 33%。也就是说，一张 2k 的图片会转换成大约 2667 个字符长的字符串。