image resampling

Three simple functions for resampling, rotating and scaling an image

There are three functions entitled imres, imrot and imsca.
- imres is a function for resampling an image to a new image.
- imrot is a function for rotating an image by an arbitrary angle (imres is pre-requisite for this function).
- imsca is a function to enlarge or playdown an image with an arbitrary scale factor (imres is pre-requiste for this function)