Sorry to see that your question hasn’t received an answer yet. On recent versions of Ubuntu with PHP 7, imageantialias is available without having to install any libraries. If you are getting false with an older version of PHP, as in the function does not exist, make sure that the GD library is installed. Otherwise, post the output of php -i in a new question. This is the equivalent of running phpinfo(); but using the CLI php.ini and config files.