How to get user's id by user's profile url?

Now when the user input his personal profile url to a textbox, such as http://www.facebook.com/Google. The form immediately show the Google logo(it's the Google's facebook paeg's logo).

If I know the page id,I ca开发者_运维问答n show the Google logo in this way:

http://graph.facebook.com/[USER_ID]/picture

But how to know the user id with any api?

You can get the user id by parsing the url and then going to https://graph.facebook.com/Google and parsing the json response. You can also parse the url to get the profile photo: https://graph.facebook.com/Google/picture