今天在centos中使用pip安装PIL死活不成功，报错：
Could not find a version that satisfies the requirement PIL (from versions: )
Some externally hosted files were ignored as access to them may be unreliable (use --allow-external PIL to allow).
No matching distribution found for PIL
但是使用pip search PIL查找，源中确实有该包：
PIL - Python Imaging Library
google之，得到如下办法（http://stackoverflow.com/questions/21242107/pip-install-pil-dont-install-into-virtualenv）：
sudo pip install PIL --allow-external PIL --allow-unverified PIL
果然成功了。
但是程序运行时又报错：
font = ImageFont.truetype(os.path.join("fonts",font_type), font_size)
ImportError: The _imagingft C module is not installed
似乎是没有安装truetype扩展之类的。那就安装吧(http://stackoverflow.com/questions/4011705/python-the-imagingft-c-module-is-not-installed):
sudo yum install freetype-devel
然后卸载、重新安装PIL
sudo pip uninstall PIL
sudo pip install PIL --allow-external PIL --allow-unverified PIL
终于搞定了
PS:之前还尝试过从官网下载PIL源码自己编译安装：
（参照：http://www.cnblogs.com/free--coder/archive/2012/09/12/2681361.html）
1.下载源码并解压：
wget http://effbot.org/downloads/Imaging-1.1.7.tar.gz
tar -xzvf Imaging-1.1.7.tar.gz
2.编译安装（注意要root权限）：
python setup.py build
python setup.py install
安装倒是成功了，但是python脚本运行时报错：
/usr/lib64/python2.7/site-packages/PIL/Image.py:81: RuntimeWarning: The _imaging extension was built for another version of Pillow or PIL
warnings.warn(str(v), RuntimeWarning)
Traceback (most recent call last):
File "captcha.py", line 3, in <module>
import Image, ImageDraw, ImageFont, ImageFilter
File "/usr/lib64/python2.7/site-packages/PIL/Image.py", line 65, in <module>
raise ImportError("The _imaging extension was built for another "
ImportError: The _imaging extension was built for another version of Pillow or PIL
似乎版本不对。。。。。
放弃了
