title: How to store signature as an image in firebase storage
body: <p>I have a form, in that form I have a signature pad. I used signature 3.2.0 package. That package consist a method toImage(). I want to store that image in the firebase storage. when I try below code.</p>
  <pre><code>fileImage = _controller.toImage() as File;
  final FirebaseStorage storage = FirebaseStorage.instance;
  final String picture = &quot;${DateTime.now().millisecondsSinceEpoch.toString()}.jpg&quot;;
  StorageUploadTask task = storage.ref().child(picture).putFile(fileImage);
  task.onComplete.then((snapshot) async{
     loadData.setSignatureURL = await snapshot.ref.getDownloadURL();
  });
  loadData.storeDetails();
  </code></pre>
  <p>I got an error <em>type 'Image' is not a subtype of type 'File' in type cast</em>.
  How can I store signature as an image/</p>