class Asciidoctor::AbstractNode

def generate_data_uri(target_image, asset_dir_key = nil)

Returns A String data URI containing the content of the target image

the image is located (default: nil)
asset_dir_key - The String attribute key used to lookup the directory where
target_image - A String path to the target image

Finally, a data URI is built which can be used in an image tag.
to ancestor paths in the filesystem. The image data is then read and converted to base64.
is set to at least SafeMode::SAFE (a condition which is true by default) to prevent access
First, and foremost, the target image path is cleaned if the document safe mode level

Public: Generate a data URI that can be used to embed an image in the output document 
def generate_data_uri(target_image, asset_dir_key = nil)
  if (ext = Helpers.extname target_image, nil)
    mimetype = ext == '.svg' ? 'image/svg+xml' : %(image/#{ext.slice 1, ext.length})
  else
    mimetype = 'application/octet-stream'
  end
  if asset_dir_key
    image_path = normalize_system_path(target_image, @document.attr(asset_dir_key), nil, target_name: 'image')
  else
    image_path = normalize_system_path(target_image)
  end
  if ::File.readable? image_path
    # NOTE pack 'm0' is equivalent to Base64.strict_encode64
    %(data:#{mimetype};base64,#{[(::File.binread image_path)].pack 'm0'})
  else
    logger.warn %(image to embed not found or not readable: #{image_path})
    %(data:#{mimetype};base64,)
    # uncomment to return 1 pixel white dot instead
    #'data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw=='
  end
end