制作lightmap的一个类。游戏制作中往往有很多小图片需要调用，一个个地load效率太低，一般是把它们拼接成一张大图片。这个类能够有效地进行图片拼接，内附说明文档。-Production of a class lightmap. Game is often a lot of small images need to call, one by one to load the efficiency is too low, generally splicing them into a big pic