Threshold dithering online
Convert any image to pure black and white (or any palette) with a simple threshold — no dithering. Free online tool with brightness and contrast controls.
About Threshold dithering
Thresholding maps each pixel straight to the nearest palette color with no dithering at all. Every value below the midpoint becomes dark, everything above becomes light.
It is the right tool for scanned documents, stencils, linocut and screen-printing prep, or any time you want flat posterized shapes. Use the brightness and contrast sliders to move the cut-off point.
Diffusion kernel
pixel < 50% ? dark : light
“*” marks the current pixel; numbers show how much of its quantization error each neighbour receives.
Best for
- Stencils and screen printing
- Cleaning up scans
- Posterized poster art
How to dither an image
- Add your image. Click Upload image, drag a file onto the preview, or paste with Ctrl/⌘+V. JPG, PNG, WebP and GIF work.
- Pick an algorithm and palette. Error diffusion (Floyd–Steinberg, Atkinson…) for photos, Bayer for a retro crosshatch.
- Tune it. Raise pixel size for chunkier pixels; adjust brightness and contrast to control which tones become dark or light.
- Download. Export a lossless PNG at up to 8× with crisp nearest-neighbour scaling.
FAQ
What is Threshold dithering?
Thresholding maps each pixel straight to the nearest palette color with no dithering at all. Every value below the midpoint becomes dark, everything above becomes light.
When should I use Threshold?
Threshold works best for: stencils and screen printing, cleaning up scans, posterized poster art.
Is DitherImage free?
Yes. DitherImage is completely free with no sign-up, no watermark and no usage limits.
Are my images uploaded to a server?
No. All processing happens locally in your browser using JavaScript and the Canvas API. Your images never leave your device.