类似网络爬虫，从一个网页“爬”到另一个网页，然后选择图片下载。多线程。 可以用来按照一定规则下载网页中的元素，如图片、网页、flash等，举例如下-download images or other stuffs by analyzing webpages, search for webpages like a spider. you can config the downloading and crawling strategy in the program