How to send an image to an api in dart/flutter?

Question

I saw other questions, but thats not what i want, i dont want to upload an image to a server, i dont want to convert to base64...

I only want to post a file in a form data or something else and get the returned info.

i have this, but has not work:

  void onTakePictureButtonPressed() {
    takePicture().then((String filePath) {
      if (mounted) {
        setState(() {
          imagePath = filePath;
          videoController?.dispose();
          videoController = null;
        });

        http.post('http://ip:8082/composer/predict', headers: {
          "Content-type": "multipart/form-data",
        }, body: {
          "image": filePath,
        }).then((response) {
          print("Response status: ${response.statusCode}");
          print("Response body: ${response.body}");
        });


        if (filePath != null) showInSnackBar('Picture saved to $filePath');
      }
    });
  }

Bostrot · Accepted Answer · 2019-07-17T08:19:39.733

40

The simplest method would be to post a multipart request like in this post and then post it to the server.

Make sure to import these in the beginning of the file:

import 'package:path/path.dart';
import 'package:async/async.dart';
import 'dart:io';
import 'package:http/http.dart' as http;
import 'dart:convert';

Add this class somewhere in your code:

upload(File imageFile) async {    
      // open a bytestream
      var stream = new http.ByteStream(DelegatingStream.typed(imageFile.openRead()));
      // get file length
      var length = await imageFile.length();

      // string to uri
      var uri = Uri.parse("http://ip:8082/composer/predict");

      // create multipart request
      var request = new http.MultipartRequest("POST", uri);

      // multipart that takes file
      var multipartFile = new http.MultipartFile('file', stream, length,
          filename: basename(imageFile.path));

      // add file to multipart
      request.files.add(multipartFile);

      // send
      var response = await request.send();
      print(response.statusCode);

      // listen for response
      response.stream.transform(utf8.decoder).listen((value) {
        print(value);
      });
    }

Then upload using:

upload(File(filePath));

In your code:

void onTakePictureButtonPressed() {
    takePicture().then((String filePath) {
      if (mounted) {
        setState(() {
          imagePath = filePath;
          videoController?.dispose();
          videoController = null;
        });

       // initiate file upload
       Upload(File(filePath));

        if (filePath != null) showInSnackBar('Picture saved to $filePath');
      }
    });
  }

edited Jul 17 '19 at 08:19

answered Jul 03 '18 at 20:23

Bostrot

5,110
3
31
41

1

I wrote a few comments to the code I posted. Basically it opens a reads the file into the bytestream, adds it to a multipart request and then sends it as a post request. All you have to do is include this class somewhere in your code and call it. – Bostrot Jul 03 '18 at 20:49
1

@MetaCode you need to import the package `import 'package:async/async.dart';` instead of `import 'dart:async';`. And this one: `import 'dart:convert';`. – Bostrot Jul 04 '18 at 07:24
Well ok, you can/should name it with a lower case character: `upload(...)` instead of `Upload(...)`. See the edited post. – Bostrot Jul 04 '18 at 20:14
I want to add one field with my multipartrequest like request .fields['name'] = DateTime.now().toIso8601String(); But, it's giving me error every time. But, if i give it a static value like request .fields['name'] = "test.png" it work. Can anybody tell me what i am doing wrong ? – Jay Mungara Oct 15 '19 at 11:56
is it possible to add headers? – user1735921 Apr 23 '20 at 12:56
@user1735921 Yes, check out the `headers` option in the docs about the [MultipartRequest](https://pub.dev/documentation/http/latest/http/MultipartRequest-class.html). – Bostrot Aug 21 '20 at 21:37
How to send file as binary – Pratik Butani Jan 19 '21 at 10:10

score 3 · Answer 2 · answered Oct 29 '19 at 17:46

3

 import 'package:dio/dio.dart'; //From 3.x.x version

    uploadImage(){
        var formData = FormData();
        formData.files.add(MapEntry("Picture", await MultipartFile.fromFile(data.foto.path, filename: "pic-name.png"), ));
        var response = await dio.client.post('v1/post', data: formdata);
    }

answered Oct 29 '19 at 17:46

Elialber Lopes

615
7
17

1

A little note: when sending an array of files to a spring boot application (which doesn't need something like "pictures[]" notation), I've found useful to follow the instructions here: https://github.com/flutterchina/dio#multiple-files-upload - read *if you don't want "[]"* – funder7 Mar 04 '21 at 12:42

score 3 · Answer 3 · answered Jun 06 '20 at 05:19

If you are sending the image to PHP Laravel Server. Try reducing the size of the image while sending it to the server. I used Image Picker package to reduce the size of the image.

var image = await ImagePicker.pickImage(source: imageSource, imageQuality: 50, maxHeight: 500.0, maxWidth: 500.0);

Then create a multipart file with that image, add it to form data, and send the form data to the server using post request with dio library. See @Elialber Lopes answer for sending the data.

It worked for me.

How to send an image to an api in dart/flutter?

3 Answers3

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