Error sending and saving image in Ionic and Flask

I am developing a project on Ionic I have a server mounted on Flask and I would like to be able to send images and treat them with this one.

I am currently doing the following:

uploadFile(img) {
let postParams = { file: img };

this.http.setDataSerializer("json");
this.http.post('http://46.101.150.118:5000/upload', postParams,
  {
    "Accept": "application/json",
    "Content-Type": "application/json"
  }
).then(data => {
  this.drawCanvas(data);
}).catch(error => {
  console.log(error);
});}

Flask Code:

@app.route('/upload', methods=['POST']) def upload():
file = request.files['file']
if file and allowed_file(file.filename):
    filename = secure_filename(file.filename)
    file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))

and in flask I receive it as "data" and not "files". Any idea how to fix it?