Dither an Image to 1-Bit Black and White
Reduce a photo to two colours using error-diffusion dithering, which scatters black and white dots to simulate the greys in between. Adjust the threshold, run a whole batch, and download without anything being uploaded.
How dithering fakes grey with two colours
Reducing an image to pure black and white by threshold alone gives a harsh, blotchy result: every pixel above a brightness cutoff turns white, everything below turns black, and all the tonal information in between is discarded. Dithering solves that by trading spatial resolution for apparent tonal depth.
Error diffusion is the technique behind it. Working across the image pixel by pixel, the algorithm rounds each one to black or white, then carries the rounding error it just made into the neighbouring pixels that have not been processed yet. A pixel pushed too dark makes its neighbours slightly lighter to compensate. Those errors spread into a fine, organic pattern of dots which, at normal viewing distance, your eye averages back into continuous greys.
This is how newspapers printed photographs for a century using nothing but black ink, and how early Macintosh screens displayed detailed images with a single bit per pixel. The look has stayed popular for its own sake: it suits zines, risograph-style prints, album artwork, e-ink displays, thermal printers, and any design wanting a tactile, low-fi feel that flat greyscale cannot deliver.
The threshold slider shifts the brightness cutoff, controlling how much of the image reads as dark versus light. It is worth nudging per image, since a bright outdoor photo and a moody interior want very different settings. Drop in several files for batch mode and a ZIP download, and keep the output as PNG so the dot pattern stays crisp.
How to dither an image
- Upload an image. High-contrast photographs with a clear subject dither best. Select several at once for batch mode.
- Adjust the threshold. Move it until the balance of light and dark reads the way you want. Every image wants a slightly different setting.
- Check the preview at full size. Dithering is a fine-detail effect, so a small preview understates how it will actually look.
- Download as PNG. Lossless output keeps the dot pattern sharp.
Raising contrast first with the filters tool usually gives a stronger result, since dithering has more to work with when tones are well separated. For a chunky retro look instead of fine dots, try the pixel art converter.
Frequently asked questions
What is dithering?
A way of representing greys using only black and white pixels. The algorithm scatters dots in a pattern your eye averages back into continuous tone at normal viewing distance.
How is it different from just converting to black and white?
A plain threshold discards everything between the extremes and looks blotchy. Error diffusion carries the rounding error into neighbouring pixels, preserving the impression of detail and gradation.
Why should I save as PNG?
PNG is lossless, so the fine dot pattern stays crisp. JPEG compression smears exactly this kind of high-frequency detail and muddies the effect.
Which images work best?
High-contrast photographs with a clear subject. Raising contrast beforehand with the filters tool gives the algorithm better separated tones to work from.
Can I dither several images at once?
Yes. Select multiple files and the tool switches to batch mode, applying the same threshold to all of them and returning a ZIP.
Are my images uploaded?
No. Processing runs on a canvas in your browser, so nothing is transmitted.
🔎 Verify it yourself: nothing uploads
Don’t take our word for it. Open your browser’s DevTools (F12 → Network tab), then run this tool on any image. You’ll see no upload request at all — your file never leaves this tab. You can even turn off Wi‑Fi once the page has loaded and keep working. Every tool on this site works the same way — all processing happens on your device.