convert table.chart to chart image by google (in prototype)

table2gchart.js

window.onload = function(){

  function Chart(table_elem, size, type) {
    this.dom = table_elem;
    this.size = size;
    this.type = type
    this.calc();
  }

  Chart.prototype.rangechars = [
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
  ];

  Chart.prototype.colors = ["FF0000", "00FF00", "0000FF", "FFFF00", "FF00FF", "00FFFF",
      "800000", "008000", "000080", "808000", "800080", "008080"];

  Chart.prototype.trs = function() {
    return this.dom.getElementsByTagName('tr');
  }

  Chart.prototype.head = function() {
    return this.rows(0);
  }

  Chart.prototype.rows = function(index) {
    var tr = this.trs()[index];
    var tds = tr.children;
    var arr = [];
    for (var i = 0, len = tds.length; i < len; i++) {
      arr.push(tds[i]);
    }
    return arr;
  }

  Chart.prototype.row_length = function() {
    return this.trs().length;
  }

  Chart.prototype.col_length = function() {
    return this.head().length;
  }

  Chart.prototype.lines_length = function() {
    return this.col_length() - 1;
  }


  Chart.prototype.calc = function() {
    if (this.data && this.data[0]) return this.data;
    this.data = [];
    for (var i = 1, len = this.row_length(); i < len; i++) {
      var r = this.rows(i);
      for (var j = 0, len2 = r.length; j < len2; j++) {
        if (!this.data[j]) this.data[j] = [];
        this.data[j].push(r[j].innerHTML.trim());
      }
    }
    return this.data;
  }

  Chart.prototype.max = function(line) {
    // TODO: cache
    return Math.max.apply(null, this.data[line+1]);
  }

  Chart.prototype.min = function(line) {
    // TODO: cache
    return Math.min.apply(null, this.data[line+1]);
  }

  Chart.prototype.yrange = function(line) {
    var margin = 0.1;
    var min = this.min(line);
    var max = this.max(line);
    var sub = max - min;
    return [line+1, min - sub*margin, max + sub*margin];
  }

  Chart.prototype.encode_unit = function(line) {
    var maxes = this.yrange(line);
    return (maxes[2] - maxes[1]) / 62;
  }

  Chart.prototype.encode_value = function(value, unit, min) {
    return Math.round((value - min)/unit);
  }

  Chart.prototype.encode = function(line) {
    var unit = this.encode_unit(line);
    var min = this.yrange(line)[1];
    var d = this.data[line+1];
    var result = this.data[line+1].map(function(x){return this.rangechars[this.encode_value(x, unit, min)]}, this);
    return result.join("");
  }

  Chart.prototype.chtt = function() {
    return encodeURIComponent(this.head()[0].innerHTML);
  }

  Chart.prototype.chdl = function() {
    return this.head().slice(1).map(function(x){return x.innerHTML}).join("|")
  }

  Chart.prototype.chco = function() {
    var num = this.lines_length();
    return this.colors.slice(0, num).join(",")
  }

  Chart.prototype.chxs = function() {
    var num = this.lines_length();
    var tmp = [];
    for (var i = 0; i < num; i++) {
      tmp.push([i+1, this.colors[i]].join(","))
    }
    return tmp.join("|");
  }

  Chart.prototype.chxr = function() {
    var tmp = [];
    for (var i = 0, l = this.lines_length(); i < l; i++) {
      tmp.push(this.yrange(i).join(","));
    }
    return tmp.join("|");
  }

  Chart.prototype.chxl = function() {
    return "0:|" + this.data[0].join("|");
  }

  Chart.prototype.chxt = function() {
    var num = this.lines_length();
    var tmp = [];
    for (var i = 0; i < num; i++) tmp.push("y");
    return "x," + tmp.join(",")
  }

  Chart.prototype.chd = function() {
    var tmp = [];
    for (var i = 0, l = this.lines_length(); i < l; i++) {
      tmp.push(this.encode(i));
    }
    return "s:" + tmp.join(",");
  }

  Chart.prototype.query = function() {
    return [
      "chs=" +(this.size||"960x240"),
      "cht=" +(this.type||"lc"),
      "chtt="+this.chtt(),
      "chco="+this.chco(),
      "chdl="+this.chdl(),
      "chxr="+this.chxr(),
      "chxt="+this.chxt(),
      "chxs="+this.chxs(),
      "chxl="+this.chxl(),
      "chd=" +this.chd()
    ].join("&");
  }

  Chart.prototype.url = function() {
    this.calc();
    return "http://chart.apis.google.com/chart?" + this.query();
  }

  // exec
  var charts = document.getElementsByClassName('chart');
  for (var i = 0, len = charts.length; i < len; i++) {
    var c = charts[i];
    var chart = new Chart(c);
    var img = document.createElement('img');
    img.src = chart.url();

    c.parentNode.insertBefore(img, c.nextSibling);
  }

}