code: func (f *Fpdf) curve(cx0, cy0, cx1, cy1, x, y float64) {
  	// Thanks, Robert Lillack, for straightening this out
  	f.outf("%.5f %.5f %.5f %.5f %.5f %.5f c", cx0*f.k, (f.h-cy0)*f.k, cx1*f.k,
  		(f.h-cy1)*f.k, x*f.k, (f.h-y)*f.k)
  }
docs: // curve outputs a single cubic Bézier curve segment from current point