CODEWITHSUNDEEP
imagefileflutterio
Zenko
Zenko

Reputation: 2559

How do I read/write image file with its original extension when you receive the image as bytes in Flutter?

Here is the problem I have:

My users can set their profile image either from Facebook (which is a jpeg or gif) or from local device (which could be png or jpg or others).

I get the image from Facebook by using:

// Get the name, email and picture
final graphResponse = await http.get(
        'https://graph.facebook.com/v4.0/me?fields=name,email,picture.width(300).height(300)&access_token=$token');

// Decode JSON
final profile = jsonDecode(graphResponse.body);
final String stringData = profile['picture']['data'];
final bytes = Uint8List.fromList(stringData.codeUnits);

And getting image from local device by:

final imagePicker = ImagePicker();

// Call image picker
final pickedFile = await imagePicker.getImage(
      source: ImageSource.gallery,
      maxWidth: MAX_WIDTH_PROFILE_IMAGE,
  );

final imageBytes = await pickedFile.readAsBytes();

Then all I got here are in bytes (Uint8List), how do I save it according to its original extension?

Then later on how do I read them again without checking its extension?

Such as with:

// Setting the filename
// Could be jpg or png or bmp or gif. 
// How to determine the extension?
final filename = 'myProfileImage'; 

// Getting App's local directory
final Directory localRootDirectory =
          await getApplicationDocumentsDirectory();
final String filePath = p.join(localRootDirectory.path, path, filename);

final file = File(filePath);

You see, when reading the file we need to specify the full filename. But how to determine the extension then ?

Upvotes: 1

Views: 772

Answers (1)

Christopher Moore
Christopher Moore

Reputation: 17143

You can avoid dealing with extensions completely by simply not setting an extension in the filename. Extensions only exist to indicate what is likely contained within a file for an OS, but they are not necessary and aren't needed in your case especially since you know that you have some kind of image data in that file and you application is probably the only thing ever using that file.

However, if you really do want to use extensions in the filename, you can use the image package. This provides a Decoder abstract class with multiple implementers for a variety of image encoding methods. To determine which method was used for your file you could check with the isValidFile of each possible decoder type that you need and write an extension accordingly.

Example:

PngDecoder png = PngDecoder();
if(png.isValidFile(data //Uint8List inputted here)) {
  print("This file is a PNG");
}

Upvotes: 3

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