ProImage is well written and easy to understand.
The templates are easy to follow with a lot of smart logic (most sections hide when they do not apply).
The source code is clearly commented and the naming makes the logic to follow - if you need to.
Most developers can add ProImage to their applications in minutes without writing a single line of code.
There are examples that clearly show you how to implement and use ProImage.
Even so - it comes with a nice help manual in compiled HTML (.chm) format.
For your convenience you can see the help file online by clicking here.