OneTaskBy Tim King · Updated
Image Dithering Tool
Floyd-Steinberg, Atkinson or Bayer Dithering Down to a Few Colours or 1-Bit
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How the Image Dithering Tool works
This image dithering tool reduces a picture to a few colours. Dithering paints an image with only a handful of colours by scattering the pixels so their average matches the original tone, the technique behind every one-bit Mac icon, early handheld game screen and printed newspaper scan. Drop in a photo, choose an error-diffusion or ordered pattern and a palette, and download the result as a crisp PNG without anything leaving your browser.
Image dithering tool: error diffusion
Floyd–Steinberg, Atkinson, Jarvis–Judice–Ninke and Stucki all work the same way: the tool walks the image pixel by pixel, snaps each one to the nearest palette colour, and pushes the difference between the wanted colour and the chosen one onto the pixels that have not been processed yet. The kernels differ in how far and in what proportions that error spreads. Floyd–Steinberg spreads it to four neighbours and is the all-round default. Atkinson, from the original Macintosh, only passes on three quarters of the error, which gives a lighter, higher-contrast image with clean whites. Jarvis and Stucki spread the error over twelve neighbours for a smoother, softer grain at the cost of a little sharpness.
Ordered dithering
The ordered options compare each pixel against a fixed threshold matrix that repeats across the image, the Bayer pattern. There is no error to carry, so the result is a regular crosshatch texture rather than organic noise. It is the look of old game consoles, early colour displays and many modern retro-styled games, and because the pattern is fixed it compresses very well and stays stable across frames of an animation. A 2×2 matrix gives only five apparent tones, 4×4 gives seventeen and 8×8 gives sixty-five, so pick a larger matrix for smoother gradients.
Palettes
Black and white produces a true one-bit image. Greys gives four levels for a softer monochrome. The handheld green palette reproduces the four shades of the classic green-screen portable console, and Sepia reads as an old print. Eight colours is the pure primary and secondary set of early home computers; Sixteen colours is the standard VGA text-mode palette. Colour dithering snaps each pixel to the nearest palette entry in RGB space and diffuses the error per channel, so a photo is reconstructed from mixtures of those few inks.
Pixel size and strength
Pixel size dithers the image at a reduced resolution and then enlarges each dot into a solid block, which keeps the pattern visible when the image is displayed small or shared on social media where fine dithering would be smoothed away. Strength scales the amount of error or threshold applied: at 100 percent you get full dithering, at 0 percent a plain posterised image with hard bands, and values between give a subtle grain over a mostly clean reduction.
FAQ
Which method should I use?
Floyd–Steinberg for a faithful photo reduction, Atkinson for the classic bright Mac look, Ordered 4×4 or 8×8 for a deliberately retro or game-like texture. Jarvis and Stucki are worth trying on smooth portraits where Floyd–Steinberg shows worm-like artefacts in the mid-tones.
Why does the output look grey when I zoom out?
That is dithering working as intended: the black and white pixels average out to grey at a distance. To keep the pattern legible at small display sizes, raise Pixel size to 2 or 3 so each dot becomes a solid block that survives downscaling.
Can I use my own palette?
The built-in palettes cover the common uses. For a custom set, reduce the image to the colours you want in an image editor, then run it here with a matching palette size to add the dither pattern; the nearest-colour snap will map each pixel to the closest of the built-in entries.
Does the PNG keep transparency?
No. Transparent areas are flattened onto white before dithering, so a logo on a transparent background comes out on a white ground. The output is opaque and lossless.
See also: all Images tools, Audio, Video & Screen, PDF, SVG, Simulations & Screensavers, Generative Art, Chart Makers, 3D Model Viewers, Drawing Pads, Mockups & 3D Making, Diagram Makers, 3D Science, Tracker Music.
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