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# -*- coding: utf-8 -*-
# Copyright (C) 2006 Edgewall Software
# Copyright (C) 2006 Alec Thomas <>
# All rights reserved.
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at
# This software consists of voluntary contributions made by many
# individuals. For the exact contribution history, see the revision
# history and logs, available at
# Author: Alec Thomas <>
import os
import random
from StringIO import StringIO
import Image
import ImageFont
import ImageDraw
import ImageFilter
from trac.core import *
from trac.util.html import html
from trac.config import *
from trac.web.api import IRequestHandler
from tracspamfilter.captcha import ICaptchaMethod
class ImageCaptcha(Component):
"""An image captcha courtesy of
implements(ICaptchaMethod, IRequestHandler)
fonts = ListOption('spam-filter', 'captcha_image_fonts', 'vera.ttf',
doc="""Set of fonts to choose from when generating image CAPTCHA.""")
font_size = IntOption('spam-filter', 'captcha_image_font_size', 25,
"""Font size to use in image CAPTCHA.""")
alphabet = Option('spam-filter', 'captcha_image_alphabet',
"""Alphabet to choose image CAPTCHA challenge from.""")
letters = IntOption('spam-filter', 'captcha_image_letters', 6,
"""Number of letters to use in image CAPTCHA challenge.""")
# IRequestHandler methods
def match_request(self, req):
return req.path_info == '/captcha/image'
def process_request(self, req):
if 'captcha_expected' not in req.session:
# TODO Probably need to render an error image here
raise TracError('No CAPTCHA response in session')
req.send_header('Content-Type', 'image/jpeg')
image = StringIO()
from pkg_resources import resource_filename
font = os.path.join(resource_filename('tracspamfilter', 'fonts'),
self.gen_captcha(image, req.session['captcha_expected'], font,
img = image.getvalue()
req.send_header('Content-Length', len(img))
# ICaptchaMethod methods
def generate_captcha(self, req):
challenge = ''.join([random.choice(self.alphabet)
for i in xrange(self.letters)])
return challenge, html.img(src=req.href('/captcha/image'), \
width='33%', alt='captcha')
def verify_captcha(self, req):
return False
def is_usable(self, req):
return True
# Internal methods
def gen_captcha(self, file, text, fnt, fnt_sz, fmt='JPEG'):
# randomly select the foreground color
fgcolor = random.randint(0,0xffff00)
# make the background color the opposite of fgcolor
bgcolor = fgcolor ^ 0xffffff
# create a font object
font = ImageFont.truetype(fnt,fnt_sz)
# determine dimensions of the text
dim = font.getsize(text)
# create a new image slightly larger that the text
im ='RGB', (dim[0]+5,dim[1]+5), bgcolor)
d = ImageDraw.Draw(im)
x, y = im.size
r = random.randint
# draw 100 random colored boxes on the background
for num in xrange(100):
# add the text to the image
d.text((3,3), text, font=font, fill=fgcolor)
im = im.filter(ImageFilter.EDGE_ENHANCE_MORE)
# save the image to a file, format=fmt)