3其中“2.gif”是树的贴图，存储为GIF文件格式。这是因为要使树的最终效果更好；要把图像的背景设置为背景透明，GIF文件格式可以存储一些背景颜色并将其转换成透明性信息，而JPG的格式不能存储透明性信息。-3 of them " 2.gif"　is a tree map, storage for the GIF file format. This is because the net effect of the tree to make better　to set the background image as the background transparent, GIF file format can store some of the background color and transparency of information into, and the JPG format can not store transparency information.