code: func Encode(w http.ResponseWriter, req *http.Request) {
  	val := func(s string) int {
  		v, _ := strconv.Atoi(req.FormValue(s))
  		return v
  	}
  
  	l := coding.Level(val("l"))
  	v := coding.Version(val("v"))
  	enc := coding.String(req.FormValue("t"))
  	m := coding.Mask(val("m"))
  
  	p, err := coding.NewPlan(v, l, m)
  	if err != nil {
  		panic(err)
  	}
  	cc, err := p.Encode(enc)
  	if err != nil {
  		panic(err)
  	}
  
  	c := &qr.Code{Bitmap: cc.Bitmap, Size: cc.Size, Stride: cc.Stride, Scale: 8}
  	w.Header().Set("Content-Type", "image/png")
  	w.Header().Set("Cache-Control", "public, max-age=3600")
  	w.Write(c.PNG())
  }
docs: // Encode encodes a string using the given version, level, and mask.