= Captcha

This captcha generator is based on the very fine work of Eric Methot 
(http://blogs.ericmethot.com/) all credit and thanks should go to him.

This fork allows you to specify a file type for captcha image generation (png or gif).

Using Captcha is a five step process

  1. Install RMagick
  2. Install the plugin 
  3. Generate a bunch of images off-line
  4. Use the helper method(s)
  5. Validate user input

The plugin has been tested on OS X 10.5 using ImageMagick @6.4.1-8_0+q16 (via MacPorts) and
the rmagick 2.5.2 gem.


== Install RMagic

Follow the instructions on their site: 
http://rmagick.rubyforge.org/install-faq.html


== Install the plugin

Installing the plugin as a submodule is as simple as issuing these commands from the
root of your rails application directory:

  To add as a submodule
  
  git submodule add git://github.com/zendesk/captcha.git
  git submodule init
  git submodule update

  To update the submodule

  git pull git://github.com/zendesk/captcha.git master
  
  Or clone and make your own changes

  git clone git@github.com:zendesk/captcha.git

Update: Using submodules is a headache to the extent where they're not really worth while.
Go for script/plugin install instead for increased happiness.

== Generate a bunch of images off-line

The reason why you don't need to generate images on the fly is that
they have been generated in advance and all you do is pick one at 
random. 

First, define a salt for your application, do this by setting the global variable 
CAPTCHA_SALT to a random string in e.g. your environment.rb
  
   CAPTCHA_SALT = 'Something really random here'

Next, generate the images by running the following rake task, this takes a while:

   rake captcha:generate COUNT=250

This will create the '/public/system/captcha' directory if it doesn't
already exist and put 250 randomly generated captcha images. 

You can specify the following parameters when running the rake task:

COUNT          - the number of images to generate, default 3
IMAGE_HEIGHT   - the height of the captcha image in pixels, default 50
IMAGE_WIDTH    - the width of the captcha image in pixels, default 260
CAPTCHA_LENGTH - the number of characters in the captcha, default 5
FILE_FORMAT    - the file type of the captcha image (png or gif)

== Use the helper methods

In your forms all you need to do is:

  <%= captcha_block %>

And add a little bit of CSS styling to get a nice looking captcha validation text field 
and image. If you don't like the way it's setup then use the other helper methods 
(see captcha_helper.rb), which are more granular.


== Validate user input

In your controller, you will need to do the following:

PostController < ApplicationController

   validates_captcha

   def create
      ...
      if captcha_validated?
         ...
      else
         ...
      end
   end
end

That's it.

Copyright (c) 2008 Zendesk, released under the MIT license