A family of symbols is defined by which much of the useful information in an image may be represented, and its choice is justified. The family includes symbols for the various commonly occuring intensity profiles that are associated with the edges of objects, and symbols for the gradual luminance changes that provide clues about a surface's shape. It is shown that these descriptors may readily be computed from measurements similar to those made by simple cells in the visual cortex of the cat. The methods that are described have been implemented, and examples are shown of their application to natural images.