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Configuration toggles

The following configuration elements can be defined (in your settings.py)

CAPTCHA_FONT_PATH

Full path and filename of a TrueType (TTF), OpenType, or pilfont font file used to render text.

Defaults to: fonts/Vera.ttf (included in the application, GPL font).

Note that your PIL installation must support TTF and/or OpenFont if you want to use these kind of glyphs (most modern distributions of PIL do.)

Note: as of version 0.4.6, CAPTCHA_FONT_PATH may be an iterable of font paths, in which case a font will be picked randomly from the list for each CAPTCHA.

CAPTCHA_FONT_SIZE

Font-size in pixels of the rendered text.

Defaults to ‘22’.

CAPTCHA_IMAGE_SIZE

Image size in pixels of generated captcha, specified by 2-tuple (width, height)

Defaults to None (automatically calculated)

CAPTCHA_LETTER_ROTATION

A random rotation in this interval is applied to each letter in the challenge text.

Defaults to (-35,35).

New in version 0.1.6: set this to None to disable letter roation.

CAPTCHA_BACKGROUND_COLOR

Background-color of the captcha. Can be expressed as html-style #rrggbb, rgb(red, green, blue), or common html names (e.g. “red”).

Defaults to: '#ffffff'

CAPTCHA_FOREGROUND_COLOR

Foreground-color of the captcha.

Defaults to '#001100'

CAPTCHA_CHALLENGE_FUNCT

String representing a python callable (i.e. a function) to use as challenge generator.

See Generators below for a list of available generators and a guide on how to write your own.

Defaults to: 'captcha.helpers.random_char_challenge'

CAPTCHA_MATH_CHALLENGE_OPERATOR

When using the math_challenge, lets you choose the multiplication operator. Use lowercase 'x' for cross sign.

Defaults to: '*' (asterisk sign)

CAPTCHA_NOISE_FUNCTIONS

List of strings of python callables that take a PIL DrawImage object and an Image image as input, modify the DrawImage, then return it.

Defaults to: ('captcha.helpers.noise_arcs','captcha.helpers.noise_dots',)

A null noise helper function useful when debugging issues is available at 'captcha.helpers.noise_null'.

CAPTCHA_FILTER_FUNCTIONS

List of strings of python callables that take a PIL Image object as input, modify it and return it.

These are called right before the rendering, i.e. after the noise functions.

Defaults to: ('captcha.helpers.post_smooth',)

CAPTCHA_WORDS_DICTIONARY

Required for the word_challenge challenge function only. Points a file containing a list of words, one per line.

Defaults to: '/usr/share/dict/words'

CAPTCHA_FLITE_PATH

Full path to the flite executable. When defined, will automatically add audio output to the captcha.

Defaults to: None (no audio output)

CAPTCHA_TIMEOUT

Integer. Lifespan, in minutes, of the generated captcha.

Defaults to: 5

CAPTCHA_LENGTH

Sets the length, in chars, of the generated captcha. (for the 'captcha.helpers.random_char_challenge' challenge)

Defaults to: 4

CAPTCHA_DICTIONARY_MIN_LENGTH

When using the word_challenge challenge function, controls the minimum length of the words to be randomly picked from the dictionary file.

Defaults to: 0

CAPTCHA_DICTIONARY_MAX_LENGTH

When using the word_challenge challenge function, controls the maximal length of the words to be randomly picked from the dictionary file.

Defaults to: 99

Note: it’s perfectly safe to specify e.g. CAPTCHA_DICTIONARY_MIN_LENGTH = CAPTCHA_DICTIONARY_MAX_LENGTH = 6 but it’s considered an error to define CAPTCHA_DICTIONARY_MAX_LENGTH to be smaller than CAPTCHA_DICTIONARY_MIN_LENGTH.

CAPTCHA_OUTPUT_FORMAT

New in version 0.1.6

Specify your own output format for the generated markup, when e.g. you want to position the captcha image relative to the text field in your form.

Defaults to: None

(Used to default to: u'%(image)s %(hidden_field)s %(text_field)s')

Note: this settings is deprecated in favor of template-based field rendering, use CAPTCHA_FIELD_TEMPLATE instead (see the Rendering section below).

CAPTCHA_TEST_MODE

New in version 0.3.6

When set to True, the string “PASSED” (any case) will be accepted as a valid response to any CAPTCHA. Use this for testing purposes. Warning: do NOT set this to True in production.

Defaults to: False

CAPTCHA_GET_FROM_POOL

By default, django-simple-captcha generates a new captcha when needed and stores it in the database. This occurs in a HTTP GET request, which may not be wished. This default behavior may also conflict with a load balanced infrastructure, where there is more than one database to read data from. If this setting is True, when a new captcha is needed, a random one will be just read from a pool of captchas saved previously in the database. In this case, the custom management command captcha_create_pool must be run regularly in intervals slightly shorter than CAPTCHA_TIMEOUT. A good value for CAPTCHA_TIMEOUT could be 1446 (24 hours and 6 minutes) when adding captchas to the pool every 24 hours, and setting CAPTCHA_GET_FROM_POOL_TIMEOUT (see below) to 5 minutes. This means that 6 minutes before the last captchas expires, new captchas will be created, and no captcha will be used whose expiration is less than 5 minutes. In this case, use a cronjob or similar to run python manage.py captcha_create_pool every 24 hours.

Defaults to: False

CAPTCHA_GET_FROM_POOL_TIMEOUT

This is a timeout value in minutes used only if CAPTCHA_GET_FROM_POOL (see above) is True. When picking up randomly from the pool, this setting will prevent to pick up a captcha that expires sooner than CAPTCHA_GET_FROM_POOL_TIMEOUT.

Defaults to: 5

Rendering

A CAPTCHA field is made up of three components:

  • The actual image that the end user has to copy from
  • A text field, that the user has to fill with the content of the image
  • A hidden field, containing the database reference of the CAPTCHA (for verification).

These three elements are rendered individually, then assembled into a single bit of HTML.

As of version 0.4.7 you can control how the individual components are rendered, as well as how all components are assembled, by overriding four templates:

  • captcha/image.html controls the rendering of the image (and optionnally audio) element
  • captcha/text_field.html controls the rendering of the text field
  • captcha/hidden_field.html controls the rendering of the hidden input
  • captcha/field.html controls the assembling of the previous three elements

These templates can be overriden in your own templates folder, or you can change the actual template names by settings CAPTCHA_IMAGE_TEMPLATE, CAPTCHA_TEXT_FIELD_TEMPLATE, CAPTCHA_HIDDEN_FIELD_TEMPLATE and CAPTCHA_FIELD_TEMPLATE, respectively.

Context

The following context variables are passed to the three “individual” templates:

  • image: The URL of the rendered CAPTCHA image
  • name: name of the field (i.e. the name of your form field)
  • key: the hashed value (identifier) of this CAPTCHA: this is stored and passed in the hidden input
  • id: the HTML id attribute to be used

The captcha/field.html template receives the following context:

  • image: the rendered (HTML) image and optionnaly audio elements
  • hidden_field: the rendered hidden input
  • text_field: the rendered text input

Note: these elements have been marked as safe, you can render them straight into your template.

Generators and modifiers

Random chars

_images/random_chars.png

Classic captcha that picks four random chars. This is case insensitive.

CAPTCHA_CHALLENGE_FUNCT = 'captcha.helpers.random_char_challenge'

Simple Math

_images/math.png

Another classic, that challenges the user to resolve a simple math challenge by randomly picking two numbers between one and nine, and a random operator among plus, minus, times.

CAPTCHA_CHALLENGE_FUNCT = 'captcha.helpers.math_challenge'

Dictionary Word

_images/dict.png

Picks a random word from a dictionary file. Note, you must define CAPTCHA_WORDS_DICTIONARY in your cofiguration to use this generator.

CAPTCHA_CHALLENGE_FUNCT = 'captcha.helpers.word_challenge'

Roll your own

To have your own challenge generator, simply point CAPTCHA_CHALLENGE_FUNCT to a function that returns a tuple of strings: the first one (the challenge) will be rendered in the captcha, the second is the valid response to the challenge, e.g. ('5+10=', '15'), ('AAAA', 'aaaa')

This sample generator that returns six random digits:

import random

def random_digit_challenge():
    ret = u''
    for i in range(6):
        ret += str(random.randint(0,9))
    return ret, ret