What is dithering?

Dithering is a technique for representing a color or tone that a display cannot reproduce exactly by mixing available colors in a pattern that the eye blends together. The word comes from the audio world — engineers in World War II added low-level noise to analog computing equipment to reduce quantization errors, calling it "dither." The technique was later adapted for digital images to smooth the harsh banding that appears when a photograph is reduced to a very limited palette, such as pure black and white or a fixed set of indexed colors.

Dithering algorithms compared

Threshold — every pixel above a luminance threshold becomes white, everything below becomes black. Fast and deterministic, but produces harsh transitions with no attempt to redistribute the rounding error. Best for high-contrast graphics, logos, and QR codes where a clean edge matters more than tonal accuracy.

Floyd–Steinberg — the quantization error at each pixel is distributed forward to its right and lower neighbors using a weighted kernel. Gradients appear as natural-looking organic noise with no visible pattern. The go-to algorithm for photographs and any image with smooth color transitions.

Bayer (ordered) — a fixed threshold matrix (typically 4×4 or 8×8) is tiled across the image, creating a regular geometric dot pattern. Produces a recognizable ordered texture rather than random noise. Popular in pixel art, retro computing aesthetics (Game Boy, ZX Spectrum), and any context where a consistent, stylized look is the goal.

Atkinson dithering

Atkinson dithering was developed by Bill Atkinson at Apple in 1984 for the original Macintosh, which had a 1-bit black-and-white display. Unlike Floyd–Steinberg, which distributes the full quantization error to neighbors, Atkinson only distributes three-quarters of the error — the remainder is discarded. This makes shadows and highlights clip to solid black or white rather than trying to represent every subtle tone, giving the output a lighter, more graphic feel that suited the Mac's high-resolution screen. Atkinson dithering is still popular for e-ink displays and stylized 1-bit art.

Where dithering is used today

Thermal receipt printers and fax machines output only black or white ink, so photographs must be dithered before transmission. E-ink displays have a limited gray palette and benefit from dithering to render photographs convincingly. 1-bit icon design and favicon creation often use dithering to hint at gradients at tiny sizes. In audio, dithering is still applied when reducing bit depth — for example, mastering a recording from 24-bit to 16-bit CD quality — to prevent the audible distortion that straight truncation would cause.