extend:
background
text
distortion
rendering
Creating your own background producer.
The background producer produces (you could have guessed) the background for the captcha. The default is a class called DefaultBackgroundImp.
Extending it can be done by either implementing the BackGroundProducer interface
or by subclassing the DefaultBackgourndImp. When sub classing there is one
method to override:
public
BufferedImage addBackground(BufferedImage image)
where the basic idea is to create a new image with the same aspect ratio as the original. First draw the background on it and then the original picture.