An image processing method operates on a colored digitised image in a
computer (2) to derive the image in abstract computer representation.
Color is used to pre-classify symbols and other features of the digital
image in order to simplify subsequent character recognition steps. By
preparing the image in accordance with rules such that a unique color is
used for all features of a defined set, and by storing those features in
the computer in computer representation in corresponding sets, once a
match has been made between a graphic feature and a stored feature, then
the color of that graphic feature is made unique to the set of stored
features containing the matched feature. The remaining graphic features
of that color then need to be compared only with the stored features in
the same set, rather than with all the stored features (of all the sets),
thus significantly reducing the character recognition processing that is
required to effect matching.