Let X denote a domain space of images and let L be a set of 'pixel
values'. Any pseudo-metric space (X,d) generates a topology 
, where the open r-spheres 
, form a base for 
. For more on topology and
metrics see e.g. [5]. In this terminology the space
of images will be denoted F(X,L).
More on the theoretical development of this work may be found in [1].
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