W HTML:

<input type="hidden" id="photoToDelete" />


            Galleria.run('#gallery',{
                extend: function() {
                    var gallery = this;

                    $('#remove_photo_link').click(function(){
                        var current = gallery.getData(gallery.getIndex());

                        var confirmation = confirm("<?php echo __('DELETE_PHOTO_CONFIRMATION')?>");
                        if (confirmation == true) {
                            $('#photoToDelete').attr('name', 'wb_product[Photos]['+gallery.getIndex()+'][photo_delete]"');
                            $('#photoToDelete').val('on');

                            $('.sf_admin_form form').submit()
                        }
                    })
                }
            });