code: func (f *Fpdf) ClipCircle(x, y, r float64, outline bool) {
  	f.ClipEllipse(x, y, r, r, outline)
  }
docs: // ClipCircle begins a circular clipping operation. The circle is centered at
  // (x, y) and has radius r. outline is true to draw a border with the current
  // draw color and line width centered on the circle's perimeter. Only the outer
  // half of the border will be shown. After calling this method, all rendering
  // operations (for example, Image(), LinearGradient(), etc) will be clipped by
  // the specified circle. Call ClipEnd() to restore unclipped operations.
  //
  // The ClipText() example demonstrates this method.