Works on both files and directories (for directories, the encrypt script calls tar first and then gpg, while for files it's just gpg).
IMPORTANT: These scripts will remove your original files or directories (if the encryption/decryption was succesful). Make sure to make copies before using it the first time, just in case it works differently on your machine for some odd reason. Also make sure that you understand the code. There is a video explaining how the scripts work so that you can see for yourself what they do.
Just download the two scripts and throw them in your ~/bin/ or your ~/.local/bin/ or wherever you put your programs.
$ encrypt some_file_or_dir
$ decrypt some_file_or_dir.gpgYou can also use wildcards like, for example:
$ encrypt *.png
$ decrypt *.png.gpgIf you want to encrypt several files into a single gpg file, put them into a directory first. Otherwise, it'll ask you to type the password once per file/dir.