class Magick::RVG::PathData

def quadratic_curveto(abs, x1, y1, x, y, *coords)

the coordinates are relative.
true the coordinates are absolute, otherwise
If abs is
Add a quadratic Bezier curveto command. 
def quadratic_curveto(abs, x1, y1, x, y, *coords)
    @path << sprintf('%s%g,%g %g,%g ', (abs ? 'Q' : 'q'), x1, y1, x, y)
    add_points(4, *coords)
end