Implementation summary
To implement resizing (or shifts)
1. create a temporary image. If resizing by factor a in x direction and b in y direction, the temporary image should be a*w by h, if the original was w by h. For shifts, use the same size.
2. resize/shift in X direction using formulas from lectures, computing pixels in the temporary image using pixels of the original image.
3. Create a final image of size a*w by b*h, if resizing, w by h if shifitng. Resize/shift in Y direction, computing the pixels of the final image using the pixels of the temporary image.