title: How do I convert jpg or png image to Blob via a Google Apps Script Web App?
body: <p>I want to http post an image from html form to google apps script web app, and then add that image to google drive.</p>
  <p>my apps script is below.</p>
  <pre><code>function doPost(e){
    var date = new Date();
    var timestamp = date.toString()
    var adress = e.parameter.adress;
    var cost = e.parameter.cost;
    var item = e.parameter.item;
    var check = e.parameter.image;
  
    //add file to drive
    var destination_id = &quot;some ID&quot;
    var destination = DriveApp.getFolderById(destination_id);
    destination.createFile(check);
  };
  </code></pre>
  <p>when I execute, it returns a error ; <code>cannot find method: createFile(String)</code></p>
  <p>I think this is because &quot;check&quot; is a string, and I want to convert the submitted image to Blob.</p>
  <p>How can I do this?</p>