$(function() 
{
  $('.ov').hover(function() 
  {
    var url = $(this).attr('src');
    if (url != null) 
    {
      var terminatorIndex = url.lastIndexOf(".");
      if ((terminatorIndex != null) && (terminatorIndex > 0)) 
      {
        var filename = url.substring(0, terminatorIndex);
        var ext = url.substring(terminatorIndex + 1);
        url = filename + "_ov." + ext;
        $(this).attr('src', url);
      }
    }
  },
  function() 
  {
    var url = $(this).attr('src');
    if (url != null) 
    {
      var urlPrimary = url.replace("_ov", "");
      $(this).attr('src', urlPrimary);
    }
  });
});