Making your own captcha is very easy. To do so you'll have to :

find a name for your captcha, for exemple mycapthca
Make a new package mycaptcha under captcha.image or captcha.sound (depending of the type of challenge)
Define two new classes in this package :
- MyCaptcha extending com.octo.captcha.image.ImageCaptcha or com.octo.captcha.sound.SoundCaptcha
  - provide a friendly constructor (for your factory)
  - implements the validateResponse method
  - implements the writeObject and readObject methods in order to make your captcha serializable
- MyCapthcaFactory extending com.octo.captcha.image.ImageCaptchaFactory or com.octo.captcha.sound.SoundCaptchaFactory
  - provide a public constructor that takes components to build captchas.
  - implement the getImageCaptcha or getSoundCaptcha method that use your contructor initialized components to construct a new captcha.

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