Interpolation algorithms in computer graphics I'm looking for an image-processing algorithm that uses interpolation (polynomial, spline, doesn't matter). I have to implement such algorithm to process a bitmap for my labs. It can't be image resizing, it must be something else. Could you give me some proposals? 
I've tried on wikipedia and google, but it's hard to filter algorithms that make use of interpolation

PS. Sorry for the tags, I can't create new ones and couldn't find existing ones that would be suitable for my question.
Some ideas:


rotate the image in 2D
compute the Radon transform.  This is used in tomography applications.
Other 2D effects, like swirling or adding ripples
Map the 2D image onto the surface a 3D shape, such as a sphere
Simulate the effect of a lens, or refraction by some other transparent 3D object in front of your bitmap
Simulate gravitational lensing by a black hole


2D image rotation is what comes to mind first as the simplest application of 2D interpolation after rescaling.  The obvious approach is to simply apply the well-known coordinate transformation; an alternative trick is to decompose the rotation into a sequence of three sheers so that only 1D interpolation is needed.

The 3D examples are more involved, since they will probably require implementation of raytracing.