add css classes to wordpress menu objects

/**
 * Filters the first and last nav menu objects in your menus to add custom classes.
 * @param object $objects An array of nav menu objects
 * @param object $args Nav menu object args
 * @return object $objects Amended array of nav menu objects with new class
 * ref link: http://thomasgriffinmedia.com/blog/2012/12/how-to-add-custom-classes-first-last-menu-items-wordpress/
 * Augmented Griffin's code with while and if loops to assign distinct css class to each menu item by Virtually Marj http://virtuallymarj.com
 * While my project only required classes for the primary menu, this code could be embellished to address any menu location or menu in your theme
 */
add_filter( 'wp_nav_menu_objects', 'vm_filter_menu_class', 10, 2 );
function vm_filter_menu_class( $objects, $args ) {

    if ( isset( $args->theme_location ) )
        if ( 'primary' !== $args->theme_location ) // Only apply the classes to the primary navigation menu
            return $objects;
    $navitems = wp_get_nav_menu_object( 'main' ); // this is the custom menu name
    $navcount = $navitems->count;
    $i=1;
    while ( $i <> $navcount ) {
    // Add distinct class to menu objects
        $objects[$i]->classes[] = 'images-menu-item-' . $i;
        $i++;
        }

    // Add "last-menu-item" class to the last menu object
    if ( $i == $navcount ) {
        $objects[count( $objects )]->classes[] = 'last-menu-item';
    }

    // Return the menu objects
    return $objects;
}