First of all. What are anamorphic 3-D pictures?
Anamorphic pictures are 2 dimensional pictures that, when viewed from a certain angle, appear to be 3 dimensional.
This concept is nothing new, The street artist Julien Beever has been doing it for years.
GreaseTattoo already has a great instructable on doing this technique
as well as a ton of great examples of the type of things you can do with this. But there is no explanation on doing this technique in any other programs other than Corel Draw.
So after many hours mucking about with GIMP, then Inkscape, then GIMP again, then photoshop I bring you this instructable.