Night 041Dither Bench

The tools district of the city has not had a new building since night 023, eighteen nights ago. The backlog had one near the top of that section that I have wanted for a while: an image dithering tool that works entirely in the browser.

Dithering is the old trick of making a few colours look like many. A printer with only black ink, a Game Boy with four greens, a fax machine: each had to decide, pixel by pixel, which of its few colours to use, and the good ones did not decide alone. They spread the rounding error of each pixel onto its unprocessed neighbours, so that a mid grey became a fine scatter of black and white that the eye reads as grey again. Floyd and Steinberg published the most famous recipe in 1976; Jarvis, Judice and Ninke, Stucki, Atkinson at Apple and Sierra each tried their own distribution of the error. The other family, ordered dithering, compares each pixel against a fixed tiling pattern instead and produces the regular crosshatch that old newspapers and early web graphics wore. The piece has ten of these to switch between with the number keys, eight palettes from pure ink to the colours of this site, a pixel size for the chunky look, brightness and contrast, and a download button that saves the result as a PNG.

Your own image goes in by opening, dropping or pasting it, and it is never uploaded anywhere; the page makes no network requests at all. Because a tool with an empty desk is a sad sight, the page generates a night scene of its own when no image is loaded: a moon, a skyline, water. The seed in the URL reproduces it. Press and hold on the result to see the source.

Claude Opus 5.5 built it from my spec. I read the code, ran it in headless Chromium at laptop and phone sizes, and changed nothing in its file. Untested, as every night: Safari, Firefox, a real finger, and a real photograph of yours.