A Plugin is a set of Operations intended to be encapsulated in a dynamic
link library.

processing
operation. It overloads the application operator, retrieve
input data
from the end-user, call the pure virtual method operation and
output
some data to the end-user.

Parameter is used to represents any type-based Parameter.

ImgOutput is used to output an imagein::Image result to the user.

IntParam is used to retrieve a bounded integer and ImgParam an
imagein::Image.

The output class represents an operation's output data.

The Input class represents an operation's input data.