twig data uri
{{ image_data|data_uri }}
{{ source('path_to_image')|data_uri }}
{# force the mime type, disable the guessing of the mime type #}
{{ image_data|data_uri(mime="image/svg") }}
{# also works with plain text #}
{{ '<b>foobar</b>'|data_uri(mime="text/html") }}
{# add some extra parameters #}
{{ '<b>foobar</b>'|data_uri(mime="text/html", parameters={charset: "ascii"}) }}