HTTP response objects returned from urllib2.urlopen(url) or requests.get(url, stream=True).raw are 'file-like' but do not support .seek() operations. As a result PIL was unable to open them as images, requiring a wrap in cStringIO or BytesIO.
Now new functionality has been added to Image.open() by way of an .seek(0) check and catch on exception :pyAttributeError or :pyio.UnsupportedOperation. If this is caught we attempt to wrap the object using io.BytesIO (which will only work on buffer-file-like objects).
This allows opening of files using both urllib2 and requests, e.g.:
Image.open(urllib2.urlopen(url))
Image.open(requests.get(url, stream=True).raw)If the response uses content-encoding (compression, either gzip or deflate) then this will fail as both the urllib2 and requests raw file object will produce compressed data in that case. Using Content-Encoding on images is rather non-sensical as most images are already compressed, but it can still happen.
For requests the work-around is to set the decode_content attribute on the raw object to True:
response = requests.get(url, stream=True)
response.raw.decode_content = True
image = Image.open(response.raw)