This is an implementation of the classic Macintosh 1-bit filter, as used by Hyperdither and HyperScan originally.
It 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
The rendered image can be rightclicked-saved. (Due to limitations of the browsers(?) you cannot drag it to the desktop)
Atkinson dithering demo app
written by Gáspár Körtesi