Share via Share via... Twitter LinkedIn Facebook Pinterest Telegram WhatsApp Yammer Reddit TeamsRecent ChangesSend via e-MailPrintPermalink × This is an old revision of the document! PHP's gd library is missing or unable to create PNG images Marc L. Smith Home Publications Grants Past courses Concurrency Teaching Publicity My Erdös Number Academic Genealogy PGP Information Bio Vassar Content AskBanner OneLogin WordPress CMS Reference Wordnik EoS Time ACM Ethics