Final answer:
The preprocessing zoom function that adds more pixels to achieve superior spatial resolution is read zoom.
Step-by-step explanation:
The type of zoom that is a preprocessing function, which provides more pixels in the region of interest resulting in superior spatial resolution, is read zoom. Unlike digital zoom, which enlarges the pixels and often leads to a pixelated image, read zoom actually uses more pixels to render the region of interest at a higher resolution. This process, as opposed to digital zoom or magnification that can degrade image quality, ensures that the image remains clear and sharp, enhancing the viewer's ability to discern fine details.