Hi,
Thank you very much for the feedback !
You should consider to download GdPicture.NET which comes with lot of snippet and demo applications.
If you liked the angle rotation feature of Paperscan, you will be impressed by many of GdPicture demos

One of them "angle rotation" is the same things that we provide in PS.
So I might ask, is the angle rotation dialog something that is coded just using GDPicture SDK or is there something extra to get this accomplished like knowing GDI or DirectX?
The feature is provided by GdPicture SDK which use its own internal c++ core, GDI32, GDI+ and sometime Direct2D (this depend on the operating system on which the SDK runs).
But frankly, this feature can easily coded from scratch using the GDI+ API via managed or unmanaged source. As my humble opinion, this is not the most exciting feature of GdPicture.
With that said, is there maybe a code demo of how this is done over in the GDPicture site?
Sure, as I said above we provide a demo application using GdPciture to accomplish such things in less than 10 lines of code. The full package can be downloaded from here:
http://www.gdpicture.com/download/downl ... urenet.php
At the start, PaperScan was a simple open source demo application snippet (less than 1 day of development have been required) demonstrating how to use GdPicture.NET SDK to build a professional scanning application. We finally decided to package it as a standalone application for internal scanning purpose, then we published it.
Cheers !
Loïc