code: func Extents(font *truetype.Font, fontSize float64, text string) (int, int) {
  	c := ftContext(font, fontSize)
  	w, h, err := c.MeasureString(text)
  	if err != nil {
  		return 0, 0
  	}
  	return int(w / 256), int(h / 256)
  }
docs: // Extents returns the *correct* max width and height extents of a string
  // given a font. See freetype.MeasureString for the deets.