Converts url("image.png") to data-uri's automatically, without having to write data-uri("image.png") in your less

npm install -g less-plugin-inline-urls

and then on the command line,

lessc file.less --inline-urls

var inline-urls-plugin = require('less-plugin-inline-urls');
less.render(lessString, { plugins: [inline-urls-plugin] })
  .then(

Browser usage is not supported at this time and is blocked on data-uri which does not work in the browser (not sure why you would want it to).