How to make slides from handwritten notes using potrace


I've never been a fan of Beamer, but handwritten slides (overheads) aren't ideal either — they smear, they aren't reproducible, and they look, well, handwritten. So, I've come up with my own process, which can be summarized as follows:

  1. Handwrite my slides on plain paper with a black marker.
  2. Scan the slides.
  3. Use potrace to convert these scans into smooth vector graphics.
  4. (Optional) Color these new slides using Adobe Illustrator or another vector graphics program.
This produces slides which look like this.

When I first started doing this, you had to compile potrace, and to do this you had to enable 64-bit compilation by setting the -m64 flag.

But now they are providing OS X binaries, so just use those. You'll want to put potrace somewhere central; I put it in /usr/local/bin.

One minor difficulty with potrace is that it doesn't read many different formats. In my setup, I get pdf scans, but have to convert them to bitmaps before I run potrace. I do that with ghostscript: 

gs -dNOPAUSE -sDEVICE=bmp16m -r200 -sOutputFile=slides.bmp scan.pdf -c quit
Once this is done, we can finally run potrace: 
potrace -b pdf -r 200 -t 5 -O 0.4 slides.bmp
The output of potrace will be a gorgeous vector graphics version of slides.bmp called slides.pdf.

Finally, I made a bash script to take care of this all: 

#!/bin/bash
gs -dNOPAUSE -sDEVICE=bmp16m -r200 -sOutputFile=$1.bmp $1.pdf -c quit
potrace -b pdf -r 200 -t 5 -O 0.4 $1.bmp
rm $1.bmp