code: func (f *Fpdf) CurveTo(cx, cy, x, y float64) {
  	f.outf("%.5f %.5f %.5f %.5f v", cx*f.k, (f.h-cy)*f.k, x*f.k, (f.h-y)*f.k)
  	f.x, f.y = x, y
  }
docs: // CurveTo creates a single-segment quadratic Bézier curve. The curve starts at
  // the current stylus location and ends at the point (x, y). The control point
  // (cx, cy) specifies the curvature. At the start point, the curve is tangent
  // to the straight line between the current stylus location and the control
  // point. At the end point, the curve is tangent to the straight line between
  // the end point and the control point.
  //
  // The MoveTo() example demonstrates this method.