Dithering

Dithering is the algorithm for preparing of image to black-white printing (old newspapers, old books) or for old displays systems. Here is 2 different implementations: general purpose with using of matrixes defined in imsh.scm library and special dithering algorithms.
Original image:

See results for Atkinson, Floyd-Steinberg, Ordered, Random, General Sierra, General Sierra Two Rows, General Sierra Low, General Floyd-Steinberg, General False Floyd-Steinberg, General Jarvis, General Stucki, General Atkinson, General Burkes:

Output image for Atkinson:

Output image for Floyd-Steiberg:

Output image for Ordered:

Output image for Random:

Output image for general Sierra:

Output image for general Sierra Two Rows:

Output image for general Sierra Low:

Output image for general Floyd-Steinberg:

Output image for general False Floyd-Steinberg:

Output image for general Jarvis:

Output image for general Stucki:

Output image for general Atkinson:

Output image for general Burkes: