I know how and I can convert the images to base64 via OS X and Linux terminals.
But I'm not sure if I can convert the fonts and the SVGs to base64 via offline OS X and Linux terminals.
I don't know any offline base64 apps that encode the images, fonts and SVG for OS X and linux. I know Coda 2 has base64 plugin, but it's bug and suffers a fail. TextMate has Emmet plugin that comes with base64 encoder, but I tried and it wasn't converted. Brackets has Emmet too, but Emmet doesn't have base64 plugin. These plugins convert only the images.