module Magick::RVG::Stretchable

def align_to_viewport(width, height, sx, sy)

Use align attribute to compute x- and y-offset from viewport's upper-left corner. 
def align_to_viewport(width, height, sx, sy)
  tx = case @align
       when /\AxMin/
         0
       when NilClass, /\AxMid/
         (width - @vbx_width * sx) / 2.0
       when /\AxMax/
         width - @vbx_width * sx
       end
  ty = case @align
       when /YMin\z/
         0
       when NilClass, /YMid\z/
         (height - @vbx_height * sy) / 2.0
       when /YMax\z/
         height - @vbx_height * sy
       end
  [tx, ty]
end