Adding javascript/jquery loading bar on PHP upload file component - repost

Project consists on adding javascript/jquery loading bar on existing upload file component. The component in wich you will add the progress bar is already installed and currently working on [login to view URL] I've got a Magento website with a custom plugin that offers the possibility to upload your picture. After loading it shows some possibilities to fit print format well. The customization we need is to add a loading bar that shows % loading of file; this is important to know the current uploading loaded, especially for heavy files. Notice: Plugin is developed with PHP.