如何在image2插件中使用ckeditor时自动将标题设置为与img标签的alt相同？

CKEDITOR.plugins.add('alttitle', {
    init: function(editor) {
        editor.on('instanceReady', function() {
            editor.dataProcessor.htmlFilter.addRules({
                elements: {
                    img: function(element) {
                        var alt = element.attributes.alt;
                        if (alt) {
                            var title = element.attributes.title;
                            if (!title) {
                                element.attributes.title = alt;
                            }
                        }
                        return element;
                    }
                }
            });
        });
    }
});

CKEDITOR.replace('editor', {
    extraPlugins: 'alttitle'
});