Uploading attachment using REST API

I am trying to upload an image file as an attachment to a submission using the instructions in this documentation. The post request is successful, however when I download and open the image attachment I encounter this error:

I used the python sudo code below. And the post request is successful however the file format seems to be wrong. I have also tried the 'Content-Type': 'image/jpeg' header with the same result.

import requests
from PIL import Image

img = Image.open('{path of image}')
binary_data = img.tobytes()

headers = {
	'Content-Type': '*/*',
	'Authorization': 'Bearer {}'.format(token)

url = 'https://private-3b1543-odkcentral.apiary-mock.com/v1/projects/projectId/forms/xmlFormId/submissions/instanceId/attachments/filename'
request = request.post(url, data=binary_data, headers=headers)

Has anyone tried uploading an attachment using the API? How did you do it and made the file format correct?