captcha.py

#http://www.bonsai-sec.com/blog/index.php/breaking-weak-captcha-in-26-lines-of-code/
from PIL import Image

img = Image.open('input.gif')
img = img.convert("RGBA")

pixdata = img.load()

# Clean the background noise, if color != black, then set to white.
for y in xrange(img.size[1]):
    for x in xrange(img.size[0]):
        if pixdata[x, y] != (0, 0, 0, 255):
            pixdata[x, y] = (255, 255, 255, 255)

img.save("input-black.gif", "GIF")

#   Make the image bigger (needed for OCR)
im_orig = Image.open('input-black.gif')
big = im_orig.resize((116, 56), Image.NEAREST)

ext = ".tif"
big.save("input-NEAREST" + ext)

#   Perform OCR using pytesser library
from pytesser import *
image = Image.open('input-NEAREST.tif')
print image_to_string(image)