Convert an imageURL to a base64 dataURL via canvas

imgURLToDataURL.es6

/**
 * Convert an imageURL to a
 * base64 dataURL via canvas
 *
 * @param   {String}  url
 * @param   {Object}  options
 * @param   {String}  options.outputFormat [outputFormat='image/png']
 * @param   {Float}   options.quality [quality=1.0]
 * @return  {Promise}
 * @docs    https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement#Methods
 * @author  HaNdTriX
 */
function imgURLToDataURL(url, options = {}) {
  return new Promise((resolve, reject) => {
    img = new Image();
    img.crossOrigin = 'Anonymous';
    img.onload = () => {
      let canvas = document.createElement('CANVAS'),
        ctx = canvas.getContext('2d'),
        dataURL;
      canvas.height = img.height;
      canvas.width = img.width;
      ctx.drawImage(img, 0, 0);
      dataURL = canvas.toDataURL(options.outputFormat, options.quality);
      resolve(dataURL);
      canvas = null;
    };
    img.src = url;
  });
}

Usage:

imgURLToDataURL('http://upload.wikimedia.org/wikipedia/commons/4/4a/Logo_2013_Google.png')
  .then(function(dataURL){
    console.log(dataURL);
  });

Compiled to ES5

/**
 * Convert an imageURL to a
 * base64 dataURL via canvas
 *
 * @param   {String}  url
 * @param   {Object}  options
 * @param   {String}  options.outputFormat [outputFormat='image/png']
 * @param   {Float}   options.quality [quality=1.0]
 * @return  {Promise}
 * @docs    https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement#Methods
 * @author  HaNdTriX
 */
'use strict';

function imgURLToDataURL(url) {
  var options = arguments[1] === undefined ? {} : arguments[1];
  return new Promise(function (resolve, reject) {
    img = new Image();
    img.crossOrigin = 'Anonymous';
    img.onload = function () {
      var canvas = document.createElement('CANVAS'),
          ctx = canvas.getContext('2d'),
          dataURL;
      canvas.height = img.height;
      canvas.width = img.width;
      ctx.drawImage(img, 0, 0);
      dataURL = canvas.toDataURL(options.outputFormat, options.quality);
      resolve(dataURL);
      canvas = null;
    };
    img.src = url;
  });
}