pendence of one primitive on a neighbouring primitive, or may have 
a dependence of n primitives at a time. The dependence may be 
structural, probabilistic, or functional (like a linear dependence). 
Image texture can be qualitatively evaluated as having one or more 
of the following properties: fine, coarse, smooth, granulated, 
rippled, mottled, irregular, random, lineated, or hummocky. Each 
of these adjectives translates into some property of the tonal 
primitives and the spatial interaction between the tonal primi- 
tives. Unfortunately, few experiments have been done attempting 
to map semantic meaning into precise properties of tonal primitives 
and their spatial distributional properties. 
To objectively use the tone and textural pattern elements, the con- 
cepts of tonal and textural feature must be explicitly defined. 
With an explicit definition, we discover that tone and texture 
are not independent concepts. They bear an inextricable relation- 
ship to one another very much like the relation between a particle 
and a wave. There really is nothing that is only particle or only 
wave. Whatever exists has both particle and wave properties and 
depending on the situation, the particle or wave properties may 
predominate. Similarly, in the image context, tone and texture 
are always there, although at times one property can dominate the 
other and we tend to speak of only tone or only texture. Hence, 
when we make an explicit definition of tone and texture, we are 
not defining two concepts: we are defining one tone-texture con- 
cept. 
The basic inter-relationships in the tone-texture concept are the 
following. When a small-area patch of an image has little variation 
of tonal primitives, the dominant property of that area is tone. 
When a small-area patch has wide variation of tonal primitives, 
the dominant property of that area is texture. Crucial in this 
distinction are the size of the small-area patch, the relative 
sizes and types of tonal primitives, and the number and placement 
or arrangement of the distinguishable primitives. As the number 
of distinguishable tonal primitives decreases, the tonal proper- 
ties will predominate. In fact, when the small-area patch is only 
the size of one resolution cell, so that there is only one discrete 
feature, the only property present is simple gray tone. As the 
number of distinguishable tonal primitives increases within the 
small-area patch, the texture property will dominate. When the 
spatial pattern in the tonal primitives is random and the gray 
tone variation between primitives is wide, a fine texture results. 
As the spatial pattern becomes more definite and the tonal regions 
involve more and more resolution cells, a coarser texture results. 
(See Picett, 1970). 
In summary, to characterize texture, we must characterize the tonal 
primitive properties as well as characterize the spatial inter-re- 
lationships between them. This implies that texture-tone is really 
a two-layered structure, the first layer having to do with speci- 
fying the local properties which manifest themselves in tonal pri- 
mitives and the second layer having to do with specifying the or- 
ganization among the tonal primitives. We, therefore, would expect 
that methods designed to characterize texture would have parts de- 
voted to analyzing each of these aspects of texture. In the review