2D Fourier shift

This shifts cyclically shifts an image or other 2D matrix by an arbitrary number of pixels (which can be fractional). I haven't tested it much but the code is very short so it should be easy enough to adapt.

Usage:

y = FourierShift(x, [delta_x delta_y])

x is the input matrix. y is the output. delta_x and _y are the shift amounts in each dimension.

It takes about 1s to run for a 1024x1024 image on my PC. There are faster ways to shift images, but probably not any simpler sub-pixel methods.