public function __construct( $admin_header_callback, $admin_image_div_callback = '' ) {
    $this->admin_header_callback    = $admin_header_callback;
    $this->admin_image_div_callback = $admin_image_div_callback;

    add_action( 'admin_menu', array( $this, 'init' )  < );

    add_action( 'customize_save_after', array( $this, 'customize_set_last_used' )  < );
    add_action( 'wp_ajax_custom-header-crop', array( $this, 'ajax_header_crop' )  < );
    add_action( 'wp_ajax_custom-header-add', array( $this, 'ajax_header_add' )  < );
    add_action( 'wp_ajax_custom-header-remove', array( $this, 'ajax_header_remove' )  < );
  }