很基本的操作，比如

import Image
im = Image.open('male.png')
im.save('test.png')

就能出错，报错信息是这样的：
Traceback (most recent call last):
File "", line 1, in
File "/usr/local/lib/python2.7/dist-packages/PIL/Image.py", line 1439, in save
save_handler(self, fp, filename)
File "/usr/local/lib/python2.7/dist-packages/PIL/PngImagePlugin.py", line 572, in _save
ImageFile._save(im, _idat(fp, chunk), [("zip", (0,0)+im.size, 0, rawmode)])
File "/usr/local/lib/python2.7/dist-packages/PIL/ImageFile.py", line 481, in _save
e = Image._getencoder(im.mode, e, a, im.encoderconfig)
File "/usr/local/lib/python2.7/dist-packages/PIL/Image.py", line 399, in _getencoder
return apply(encoder, (mode,) + args + extra)

但是

im.show()

是可以看到图片的。
搜了好久都没搜到类似的问题...