PIL: Thumbnail and end up with a square image

Paste the image into a transparent image with the right size as a background

from PIL import Image
size = (36, 36)
image = Image.open(data)
image.thumbnail(size, Image.ANTIALIAS)
background = Image.new('RGBA', size, (255, 255, 255, 0))
background.paste(
    image, (int((size[0] - image.size[0]) / 2), int((size[1] - image.size[1]) / 2))
)
background.save("output.png")

EDIT: fixed syntax error

from PIL import Image

import StringIO

def thumbnail_image():
    image = Image.open("image.png")
    image.thumbnail((300, 200))
    thumb_buffer = StringIO.StringIO()
    image.save(thumb_buffer, format=image.format)
    fp = open("thumbnail.png", "w")
    fp.write(thumb_buffer.getvalue())
    fp.close()

PIL already has a function to do exactly that:

from PIL import Image, ImageOps
thumb = ImageOps.fit(image, size, Image.ANTIALIAS)