Image Download Buttom

You can use something like this in a plug-in, sets headers. Works for pdf anyway.

$path = "path to file";

        if(!file_exists($path))
            throw new exception("File does not exist");

        header("Content-type: File MIME type");
        header("Content-disposition: attachment; filename=\"Name of the file\"");
        header('Content-Transfer-Encoding: binary');
        header("Content-length: " . filesize($path));
        header('Expires: 0');

        // check for IE only headers
        if (isset($_SERVER['HTTP_USER_AGENT']) && (strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE') !== false))
        {
          header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
          header('Pragma: public');
        } else {
          header('Pragma: no-cache');
        }

        readfile($path);

Thinking about it there most probably is a plug-in in the word-press plug-in repo that already does this. Look for ‘file download’ or related terms.

If you don’t already, I’d recommend learning some PHP. You would need to create a custom plugin, which serves images from php from a url like /image?id=the_image_id. The above code tells the browser to download the file by setting it as an attachment.

You need to take care doing this as it can easily create a security hole. The application I took the code from will only serve a limited number of files defined in a database. Without care, a script like this could allow someone to download any file php has access to, like your wordpress config.