class Magick::RVG::Image

def align_to_viewport(scale)
    tx = case @align
            when 'none', /\AxMin/
                0
            when NilClass, /\AxMid/
                (@width - @image.columns*scale) / 2.0
            when /\AxMax/
                @width - @image.columns*scale
    end
    ty = case @align
            when 'none', /YMin\z/
                0
            when NilClass, /YMid\z/
                (@height - @image.rows*scale) / 2.0
            when /YMax\z/
                @height - @image.rows*scale
    end
    return [tx, ty]
end