Create images with sub-pixel shift
The science of finding values in between those points where you actually have samples is called Interpolation. 

It's a rich field, and every signal processing toolkit (be it Matlab or OpenCV, or …) has functions for it.

Picking the right interpolator has a lot to do with the nature of your input, and the purpose of you doing the interpolation  – so, no general advice can be given on what specific interpolator to use.