code: func (f *Fpdf) TransformScale(scaleWd, scaleHt, x, y float64) {
  	if scaleWd == 0 || scaleHt == 0 {
  		f.err = fmt.Errorf("scale factor cannot be zero")
  		return
  	}
  	y = (f.h - y) * f.k
  	x *= f.k
  	scaleWd /= 100
  	scaleHt /= 100
  	f.Transform(TransformMatrix{scaleWd, 0, 0,
  		scaleHt, x * (1 - scaleWd), y * (1 - scaleHt)})
  }
docs: // TransformScale generally scales the following text, drawings and images.
  // scaleWd and scaleHt are the percentage scaling factors for width and height.
  // (x, y) is center of scaling.
  //
  // The TransformBegin() example demonstrates this method.