using a PIL.Image to write out to the response stream

pil_image_direct_to_response_stream.py

from StringIO import StringIO
from google.appengine.api import images

out_stream = StringIO()

# put the data into a StringIO instance so we can manipulate it with PIL.Image
original_image_data = StringIO(source_img_response.read())
editable_image = Image.open(original_image_data)
editable_image.thumbnail((width, height), Image.ANTIALIAS)
editable_image.save(out_stream, "PNG")

# write the thumbnail stream directly out to the response instead of making another
# request back to <thumbnail_deck_url>/data/Thumbnail/SlideX.resize.HxW.png
writable_bytes = out_stream.getvalue()
self.response.out.write(writable_bytes)