code: func (f *Fpdf) SetFillSpotColor(nameStr string, tint byte) {
  	var clr spotColorType
  	var ok bool
  
  	clr, ok = f.getSpotColor(nameStr)
  	if ok {
  		f.color.fill.mode = colorModeSpot
  		f.color.fill.spotStr = nameStr
  		f.color.fill.str = sprintf("/CS%d cs %.3f scn", clr.id, float64(byteBound(tint))/100)
  		f.colorFlag = f.color.fill.str != f.color.text.str
  		if f.page > 0 {
  			f.out(f.color.fill.str)
  		}
  	}
  }
docs: // SetFillSpotColor sets the current fill color to the spot color associated
  // with nameStr. An error occurs if the name is not associated with a color.
  // The value for tint ranges from 0 (no intensity) to 100 (full intensity). It
  // is quietly bounded to this range.