I'm curious what exactly "render" means in your context? Phantom.js is headless, so it would be futile to be simply rendering GIFs and JPGs within the browser I assume?
Imagine it like a web page to PNG converter. This doesn't need a desktop/display attached to do that. That's what "render" means in a headless context.
Ah. I get it. Brain did not parse "render" as the output side, but rather the input, so I was trying to figure out why they used phantom.js as an elaborate image format converter.