12. A non-transitory computer-readable medium having instructions encoded thereon which, when executed by a processing device, causes the processing device to perform operations comprising: receiving an image file representing an image comprising text, the text comprising a plurality of letters; generating a data structure comprising a set of nodes, wherein the set of nodes comprises a plurality of parent nodes, each of the parent nodes associated with one or more terminal nodes, wherein each of the terminal nodes represents an initial letterform class of the plurality of letters and each of the parent nodes represents an initial letterform class group of initial letterform classes, wherein a first initial letterform class group represented by a first parent node is associated with a plurality of initial letterform classes of different letters having common letter properties; and determining a set of final letterform classes by: comparing two parent nodes of the set of nodes; and merging the two parent nodes of the set of nodes based on the comparison.
12. A non-transitory computer-readable medium having instructions encoded thereon which, when executed by a processing device, causes the processing device to perform operations comprising: receiving an image file representing an image comprising text, the text comprising a plurality of letters; generating a data structure comprising a set of nodes, wherein the set of nodes comprises a plurality of parent nodes, each of the parent nodes associated with one or more terminal nodes, wherein each of the terminal nodes represents an initial letterform class of the plurality of letters and each of the parent nodes represents an initial letterform class group of initial letterform classes, wherein a first initial letterform class group represented by a first parent node is associated with a plurality of initial letterform classes of different letters having common letter properties; and determining a set of final letterform classes by: comparing two parent nodes of the set of nodes; and merging the two parent nodes of the set of nodes based on the comparison. 16. The non-transitory computer-readable medium of claim 12 , further comprising generating a text file representing the text based on the set of final letterform classes.