orderedordered ditheringdithering

Dithering represents a range of tones with fewer output levels by mixing them in a pattern. Ordered dithering does this with a fixed threshold matrix instead of spreading error between pixels.

#the bayer matrix

The 4×4 Bayer matrix orders 16 thresholds so neighbouring values are as far apart as possible:

 0   8   2  10
12   4  14   6
 3  11   1   9
15   7  13   5

For a pixel at (x, y) with brightness v in [0, 1]:

t = (M[y % 4][x % 4] + 0.5) / 16
out = v > t ? 1 : 0

#properties

• Deterministic and parallel. Every pixel is independent, so it's trivial on a GPU.
• Stable under animation. The pattern doesn't crawl between frames the way error diffusion can.
• Visible texture. The cross-hatch is regular, which reads as "retro" rather than as noise.

#compared with error diffusion

Floyd-Steinberg pushes each pixel's rounding error onto its unprocessed neighbours. It preserves detail better but is sequential and produces worm-like artefacts in flat areas.

#next

Try the same thresholds on characters instead of pixels: map each threshold band to a glyph and compare against plain luminance ramps.