I need to build a simple UI to georeference a jpg or gif image with a worldfile. Simple stuff if you are using ArcSomething or MapInfo. However, I can't seem to figure out how to do the affine transformation using more than 2 control points. Using a linear equation (top left coordinates and bottom right coordinates) seems easy enough, but what type of formula (and how) would I plug in more than 2 control points? I would hope the system could use control points that are not corners to make it easier on the user. The system is being developed in VB.net and yes, I realize applications like OziExplorer can do this and unfortunately, I need to reinvent the wheel. Any thoughts on how to get started on this?
Thanks in advance,