use this URL : "https://twitter.com/(userName)/profile_image?size=original"
If you are using TWitter SDK you can get the user name when logged in, with TWTRAPIClient, using TWTRAuthSession.
This is the code snipe for iOS:
if let twitterId = session.userID{
let twitterClient = TWTRAPIClient(userID: twitterId)
twitterClient.loadUser(withID: twitterId) {(user, error) in
if let userName = user?.screenName{
let url = "https://twitter.com/\(userName)/profile_image?size=original")
}
}
}