Uri.dataFromBytes(List<int> bytes, {mimeType: "application/octet-stream", Map<String, String> parameters, percentEncoded: false})

Creates a data: URI containing an encoding of bytes.

Defaults to Base64 encoding the bytes, but if percentEncoded is true, the bytes will instead be percent encoded (any non-ASCII or non-valid-ASCII-character byte is replaced by a percent encoding).

To read the bytes back, use UriData.contentAsBytes.

It defaults to having the mime-type application/octet-stream. The mimeType and parameters are added to the created URI. If any of these contain characters that are not allowed in the data URI, the character is percent-escaped. If the character is non-ASCII, it is first UTF-8 encoded and then the bytes are percent encoded.

Source 

factory Uri.dataFromBytes(List<int> bytes,
                          {mimeType: "application/octet-stream",
                           Map<String, String> parameters,
                           percentEncoded: false}) {
  UriData data = new UriData.fromBytes(bytes,
                                       mimeType: mimeType,
                                       parameters: parameters,
                                       percentEncoded: percentEncoded);
  return data.uri;
}