Custom CAPTCHA

This class can be used to display images for CAPTCHA validation. It can display an image with a random text that the user needs to read and enter in a form to authorize the access to resources to real human users. The text is rendered over a given obfuscation image. The length, font and size of the text is configurable. The validation text is stored in a session variable for posterior validation. The validation image format can be either GIF, JPEG or PNG.