code: func (f *Fpdf) Curve(x0, y0, cx, cy, x1, y1 float64, styleStr string) {
  	f.point(x0, y0)
  	f.outf("%.5f %.5f %.5f %.5f v %s", cx*f.k, (f.h-cy)*f.k, x1*f.k, (f.h-y1)*f.k,
  		fillDrawOp(styleStr))
  }
docs: // Curve draws a single-segment quadratic Bézier curve. The curve starts at
  // the point (x0, y0) and ends at the point (x1, y1). The control point (cx,
  // cy) specifies the curvature. At the start point, the curve is tangent to the
  // straight line between the start point and the control point. At the end
  // point, the curve is tangent to the straight line between the end point and
  // the control point.
  //
  // styleStr can be "F" for filled, "D" for outlined only, or "DF" or "FD" for
  // outlined and filled. An empty string will be replaced with "D". Drawing uses
  // the current draw color, line width, and cap style centered on the curve's
  // path. Filling uses the current fill color.
  //
  // The Circle() example demonstrates this method.