1. 从sprite sheet里把每一个sprite到处成image，然后用texture packer就可以生成plist
http://www.alferdspritesheetunpacker.forkandbeard.co.uk/forkandBeard/apps/AlferdSpritesheetUnpacker/Download.aspx
2. 批量去除纯色背景的方法：
http://graphicdesign.stackexchange.com/questions/16120/batch-replacing-color-with-transparency