I wanted to see if I could blur screenshots for my lockscreen faster than ImageMagick. This is faster, but ultimately the slowness comes from reading/writing to pngs, and the fact that i3lock only accepts pngs. In reality, using i3lock-color is a better option than this, but it was a fun little exercise.
The actual blurring code is wholesale converted from http://blog.ivank.net/fastest-gaussian-blur.html