Post and image, as in the following examples.

curl -i -X POST -H "Content-Type: multipart/form-data" -F "file=@myimage.jpg" -F "usr={username}" -F "pass={password}" -F "langid={selected lang}" 'https://nyx.athenarc.gr/advent/api'

• usr: "The username of the user"
• pass: "The password of the user"
• langid: "el" or "en"