see hidden areas in xkcd 1608 - requires bottle.py, PIL(low), numpy

funproxy.py

#!/usr/bin/env python
import StringIO
import numpy as np
from bottle import route
from bottle import run
from bottle import abort
import Image
import requests


base_url = 'http://xkcd.com/'

@route('/<image:path>')
def proxy(image):
    resp = requests.get(base_url + image)
    if resp.status_code != 200:
        abort(resp.status_code)
    if 'png' in resp.headers['content-type']:
        return munge_png(resp.content)
    return resp.content


def munge_png(png_in):
    im = Image.open(StringIO.StringIO(png_in))
    im = im.convert('RGBA')
    
    data = np.array(im)   # "data" is a height x width x 4 numpy array
    red, green, blue, alpha = data.T # Temporarily unpack the bands for readability
    
    # Replace white with red... (leaves alpha values alone...)
    deception = (red == 1) & (blue == 1) & (green == 1)
    data[..., :-1][deception.T] = (255, 0, 0) # Transpose back needed
    
    im2 = Image.fromarray(data)
    png_out_io = StringIO.StringIO()
    im2.save(png_out_io, format='PNG')
    return png_out_io.getvalue()

run(host='localhost', port=8080, debug=True)