The classic Macintosh 1-bit filter, as used by HyperDither.

This project was originally created 2010-2016 by @gazs (sources, live demo).

Compares every pixel to 50% grey, then changes them to either black or white. The difference between the input and the output is then distributed to the neighbouring pixels as follows (X is the current pixel):

     X  1/8 1/8
1/8 1/8 1/8
    1/8

Example screenshot:

Requires npm.

Start a local web server to run the demo app:

./start.sh

This code uses Drag and Drop events, WebWorkers, and the FileReader API.