code: func (f *Fpdf) TransformRotate(angle, x, y float64) {
  	y = (f.h - y) * f.k
  	x *= f.k
  	angle = angle * math.Pi / 180
  	var tm TransformMatrix
  	tm.A = math.Cos(angle)
  	tm.B = math.Sin(angle)
  	tm.C = -tm.B
  	tm.D = tm.A
  	tm.E = x + tm.B*y - tm.A*x
  	tm.F = y - tm.A*y - tm.B*x
  	f.Transform(tm)
  }
docs: // TransformRotate rotates the following text, drawings and images around the
  // center point (x, y). angle is specified in degrees and measured
  // counter-clockwise from the 3 o'clock position.
  //
  // The TransformBegin() example demonstrates this method.