Forum: Ruby on Rails Show thumbnail preview of image before upload

Is there any ruby way to show thumbnail preview of image before upload?

Using below javascript, I can achieve this

     window.URL = window.URL || window.webkitURL;

  var fileElem = document.getElementById("fileElem");

  function handleFiles(files) {
    var img = document.getElementById("image-preview");

    if (!files.length) {
      img.src = "/img/default-profile-image.png";
    } else {
      img.src = window.URL.createObjectURL(files[0]);
      img.height = 60;
      img.onload = function(e) {
        window.URL.revokeObjectURL(this.src);
      }
    }

  }

but I want to keep the thumbnail image in the case of validation fails.

Please help me....

Thanks in advance,
Avantec

2012/9/25 Avantec Van <lists@ruby-forum.com>:
> Is there any ruby way to show thumbnail preview of image before upload?

No!

There can't be! Ruby needs you to have that image on the server to
generate a thumb of it, but before the upload it is not on the server.

What you try here, is not possible in PHP, whatever.NET or any other
kind of server-side-scripting-language.

But wait Once, I stumbled upon a project, that is a ruby-interpreter
implemented in JavaScript, but can't remember its name. With that it
would be possible to generate the preview, but not to save it
anywhere