This function is the same as xfun::base64_uri() (only with a
different function name). It can encode an image file as a base64 string,
which can be used in the img tag in HTML.
uri = image_uri(file.path(R.home("doc"), "html", "logo.jpg"))
if (interactive()) {
cat(sprintf("", uri), file = "logo.html")
browseURL("logo.html") # you can check its HTML source}