mac 安装PIL
PIL是python Image library
在mac终端中通过以下命令安装：

# downloadcurl -O -L http://effbot.org/media/downloads/Imaging-1.1.7.tar.gz# extracttar -xzf Imaging-1.1.7.tar.gzcd Imaging-1.1.7# build and installpython setup.py buildsudo python setup.py install# or install it for just you without requiring admin permissions:# python setup.py install --user