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.