The Mathematics of Symbol Recognition. I wonder what Mathematics is behind handwriting and symbol recognition. I was using Detexify just now and it struck me that a distinction could be made between $\varsigma$ (a variant of the Greek letter sigma), $\zeta$ (the Greek letter zeta), and $\xi$ (the Greek letter xi). I was thinking that it'd be some combination of Topology, Graph Theory, and Knot Theory. > How do such recognition things like Detexify work, mathematically speaking? A detailed answer would be great.

Detexify's implementation is explained here: < Briefly, it is a $k$-nearest neighbors classifier with hand-tuned features. Nothing fancy, no topology:

> The features I use (at the time of writing) are number of strokes, point density and directional features.