diff -r 058bb3dc685f -r 0b59724cb3f2 cubicweb/web/captcha.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/web/captcha.py	Sat Jan 16 13:48:51 2016 +0100
@@ -0,0 +1,98 @@
+# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of CubicWeb.
+#
+# CubicWeb is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
+"""Simple captcha library, based on PIL. Monkey patch functions in this module
+if you want something better...
+"""
+
+__docformat__ = "restructuredtext en"
+
+from random import randint, choice
+from io import BytesIO
+
+from six.moves import range
+
+from PIL import Image, ImageFont, ImageDraw, ImageFilter
+
+
+from time import time
+
+from cubicweb import tags
+from cubicweb.web import ProcessFormError, formwidgets as fw
+
+
+def pil_captcha(text, fontfile, fontsize):
+    """Generate a captcha image. Return a PIL image object.
+
+    adapted from http://code.activestate.com/recipes/440588/
+    """
+    # randomly select the foreground color
+    fgcolor = randint(0, 0xffff00)
+    # make the background color the opposite of fgcolor
+    bgcolor = fgcolor ^ 0xffffff
+    # create a font object
+    font = ImageFont.truetype(fontfile, fontsize)
+    # determine dimensions of the text
+    dim = font.getsize(text)
+    # create a new image slightly larger that the text
+    img = Image.new('RGB', (dim[0]+5, dim[1]+5), bgcolor)
+    draw = ImageDraw.Draw(img)
+    # draw 100 random colored boxes on the background
+    x, y = img.size
+    for num in range(100):
+        draw.rectangle((randint(0, x), randint(0, y),
+                        randint(0, x), randint(0, y)),
+                       fill=randint(0, 0xffffff))
+    # add the text to the image
+    draw.text((3, 3), text, font=font, fill=fgcolor)
+    img = img.filter(ImageFilter.EDGE_ENHANCE_MORE)
+    return img
+
+
+def captcha(fontfile, fontsize, size=5, format='JPEG'):
+    """Generate an arbitrary text, return it together with a buffer containing
+    the captcha image for the text
+    """
+    text = u''.join(choice('QWERTYUOPASDFGHJKLZXCVBNM') for i in range(size))
+    img = pil_captcha(text, fontfile, fontsize)
+    out = BytesIO()
+    img.save(out, format)
+    out.seek(0)
+    return text, out
+
+
+class CaptchaWidget(fw.TextInput):
+    def render(self, form, field, renderer=None):
+        # t=int(time()*100) to make sure img is not cached
+        src = form._cw.build_url('view', vid='captcha', t=int(time()*100),
+                                 captchakey=field.input_name(form))
+        img = tags.img(src=src, alt=u'captcha')
+        img = u'<div class="captcha">%s</div>' % img
+        return img + super(CaptchaWidget, self).render(form, field, renderer)
+
+    def process_field_data(self, form, field):
+        captcha = form._cw.session.data.pop(field.input_name(form), None)
+        val = super(CaptchaWidget, self).process_field_data(form, field)
+        if val is None:
+            return val # required will be checked by field
+        if captcha is None:
+            msg = form._cw._('unable to check captcha, please try again')
+            raise ProcessFormError(msg)
+        elif val.lower() != captcha.lower():
+            msg = form._cw._('incorrect captcha value')
+            raise ProcessFormError(msg)
+        return val