class Magick::RVG

the canvas not covered by the image with the background color.
image proportions. Center the image on the canvas. Color any part of
[:fit] Scale the image to fit within the canvas while retaining the
[:tiled] Tile the image across the canvas.
[:scaled] Scale the image to the canvas width and height.
How to position the background image on the canvas. One of the following symbols:

def background_position=(pos)
  warn 'background_position= has no effect in nested RVG objects' if @nested
  bg_pos = pos.to_s.downcase
  raise ArgumentError, "background position must be `scaled', `tiled', or `fit' (#{pos} given)" unless %w[scaled tiled fit].include?(bg_pos)
  @background_position = bg_pos.to_sym
end