How to upload a screenshot using html2canvas?

Question

Using html2canvas how can I save a screen shot to an object? I\'ve been exploring the demos, and see that the function to generate the screenshot is generated as follows:

Answer 1

I have modified and annotated the method from this answer. It sends only one file, with a given name, composed from a element.

if (!('sendAsBinary' in XMLHttpRequest.prototype)) {
  XMLHttpRequest.prototype.sendAsBinary = function(string) {
    var bytes = Array.prototype.map.call(string, function(c) {
      return c.charCodeAt(0) & 0xff;
    });
    this.send(new Uint8Array(bytes).buffer);
  };
}

/*
 * @description        Uploads a file via multipart/form-data, via a Canvas elt
 * @param url  String: Url to post the data
 * @param name String: name of form element
 * @param fn   String: Name of file
 * @param canvas HTMLCanvasElement: The canvas element.
 * @param type String: Content-Type, eg image/png
 ***/
function postCanvasToURL(url, name, fn, canvas, type) {
  var data = canvas.toDataURL(type);
  data = data.replace('data:' + type + ';base64,', '');

  var xhr = new XMLHttpRequest();
  xhr.open('POST', url, true);
  var boundary = 'ohaiimaboundary';
  xhr.setRequestHeader(
    'Content-Type', 'multipart/form-data; boundary=' + boundary);
  xhr.sendAsBinary([
    '--' + boundary,
    'Content-Disposition: form-data; name="' + name + '"; filename="' + fn + '"',
    'Content-Type: ' + type,
    '',
    atob(data),
    '--' + boundary + '--'
  ].join('\r\n'));
}