[ptx] new reference for stitching algorithms

[Rik Littlefield]

Developers of stitching software, please be aware of this reference:

http://grail.cs.washington.edu/projects/photomontage/

The paper at

http://grail.cs.washington.edu/projects/photomontage/photomontage.pdf

illustrates several very interesting and impressive results.

It is titled "Interactive Digital Photomontage", but the computational 
techniques seem amenable to purely batch processes as well.  See figures 
2, 8, and 9 of the paper for example.

--Rik