程序主要是利用计算机图形学中的分形技术画出一棵树，然后实现树的忽大忽小，忽远忽近，而树的背景不变。运行程序后，按Esc键即可退出。-Program is the use of computer graphics technology to draw a fractal tree, and then realize the tree suddenly suddenly small, suddenly away suddenly near, and trees in the background u