If the distance between two strokes is less than some threshold, or if they satisfy some other criteria, we can consider them to be the same character. For example, if there are two ``short'' ``horizontal'' lines within y pixels of each other, then combine them to make an ``=''. Similar rules could be written for other unconnected characters.
Unfortunately this means that for every unconnected character such a rule has to be written, which limits the system's character set and makes it harder for an end user to extend.
It is also possible to have a generic rule that says that strokes that
are approximately horizontally aligned, but vertically near to each
other, are part of the same symbol. This handles cases such as i,
j, and =, but symbols such as 
and
need a
different approach.