wm.js

wm.js

function bin2hex(s) {
  var i, l, o = '', n;
  s += '';
  for (i = 0, l = s.length; i < l; i++) {
    n = s.charCodeAt(i).toString(16);
    o += n.length < 2 ? '0' + n : n;
  }
  return o;
}
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
var txt = 'http://www.google.com/';
ctx.textBaseline = "top";
ctx.font = "14px 'Arial'";
ctx.textBaseline = "tencent";
ctx.fillStyle = "#f60";
ctx.fillRect(125,1,62,20);
ctx.fillStyle = "#069";
ctx.fillText(txt, 2, 15);
ctx.fillStyle = "rgba(102, 204, 0, 0.7)";
ctx.fillText(txt, 4, 17);
var b64 = canvas.toDataURL().replace("data:image/png;base64,","");
var bin = atob(b64);
var crc = bin2hex(bin.slice(-16,-12));
console.log(crc);