This is the Captcha library ported from Kohana 2.3.x to 3.x. Very little has changed API-wise, although there have been a few changes.
Instantiate a captcha:
$captcha = Captcha::instance();
Instantiate using your own config group (other than 'default'):
$captcha = Captcha::instance('myconfig');
Render a captcha:
Validate the captcha:
By default image-based captchas are rendered with HTML, the HTML is a very simple tag. If you want to handle your own rendering of the captcha simply set the first parameter for render() to FALSE: