Way to get valid NetworkCredentials object from SPUser using forms based authentication?

I am developing a SharePoint 2013 application with Visual Studio. I am attempting to use the SharePoint client API to set the user's profile picture, since this API seems better than the server API. I've read here how you can get a NetworkCredentials object, but that solution depends on the WindowsIdentity object being valid. I am not getting a valid WindowsIdentity object when the user logged in via forms based authentication, but I do get a valid WindowsIdentity object when the user is logged in via Windows authentication.

Is there a way to get a NetworkCredentials object that contains credentials of the logged in user with forms based authentication, or am I stuck with the server APIs?