A break from regularly scheduled programming.

I got to thinking about handwriting while on a walk yesterday. Like so many things we do, it’s beautiful how we seamlessly coordinate half a dozen joints to externalize our memory.

I also find it interesting how most people have an identifiable scrawl. Mine is pure slop, but I suspect I could pick it out of a lineup. I bet this is true for most folks.

This got me wondering how hard it would be to generate a unique “hand” for a computer. My initial thought was to model the major joints and try to actuate these joints to generate letters. I’m not sure if this is already a Reinforcement Learning benchmark, but it’s closely related to a number of physics-based robotics tasks that are RL benchmarks.

After some toying around, I decided to go even simpler. You can see my proof of concept below:

You can click the “rewrite” button to regenerate the letters.

I developed this little widget using JavaScript and HTML5 canvas. Canvas gives you a stroke based API for generating lines and curves, and I ported the strokes I use to write these letters by hand over to this API. I then generate some Gaussian noise to perturb the start, curve, and end of each stroke. This adds slop and gives it a bit of a human feel. I find the results quite pleasing even though it took very little code to achieve.

Further extensions I might explore:

  • Correlated errors - When I write an “E”, first I write an “L” and then add the middle and top horizontal bar. I suspect the errors for the horizontal bars are correlated (i.e. they might slant upward or they might slant downward, but they will probably all slant in the same direction).

  • Scale error by distance - I suspect error increases the further you move your pen (a corollary of Fitts’s Law). Thus long strokes (or long moves that don’t generate lines) should be noisier than short strokes.

  • Scale error by direction - Suppose you’re moving the pen vertically. I suspect your going to get more error in the vertical direction than you are in the horizontal direction. I believe this generalizes to any axis of motion.

Finally, if you happen to be Drake and you need a new album cover, let me know and I’ll definitely flesh out the text generation engine!