# Regular Pyramids

There are two terms to describe the structure of a regular pyramid:

- the
**reduction factor**, which determines the rate by which the number of cells decrease from level to level, and - the
**reduction window**, which associates a set of cells of the level directly below to every (higher level) cell. It covers the area of its associated cell. Reduction windows are mostly rectangular shaped.

A pyramid is defined by its structure and its operation, which is responsible for the bottom-up information flow within the pyramid. This operation is called the

**reduction function**.

In gray level pyramids, the contents of cells are gray values or color vectors. Every level of the pyramid is a picture. Different reduction functions can be used to fill the bottom-up cells of the pyramid.

Examples |