Threshold
Pure black and white with one cutoff
Runs in your browser. Files never leave your device.
How to use Threshold
- Choose or drop your images. You can add several at once.
- Adjust the settings and check the preview.
- Download the result, or every file at once as a ZIP.
About this tool
Turn any image into pure black and white with a single cutoff: everything lighter becomes white and everything darker becomes black. The automatic mode finds the best cutoff for your picture using Otsu’s method.
It is useful for stencils, signatures, scanned documents and graphic poster looks. Speckle removal cleans up noisy scans, and you can swap black and white for any two colors.
- Works on your device. Nothing is uploaded.
- Free, with no sign-up and no watermark.
- No limits on file count or size beyond what your device can handle.
Questions and answers
How is the automatic threshold chosen?
Otsu’s method looks at the brightness histogram and picks the cutoff that best separates the image into a dark and a light group.
How do I clean up a scanned signature?
Keep the automatic threshold on, raise “Remove speckles” a little and set edge softness to 0 for crisp pixels. Save as PNG for a small, sharp file.
Why are the edges slightly gray?
Edge softness anti-aliases the border between black and white so curves look smooth. Set it to 0 if you need exactly two colors.
Is Threshold free?
Yes. Every tool on ImgImage is free to use, with no sign-up, no watermark and no limit on how many files you process.
Are my files uploaded anywhere?
No. Your files are processed by your own browser and never leave your device. Nothing you open here is sent to a server.
Does it work on my phone?
Yes. It works in any modern browser on phones, tablets and computers. Large files are processed faster on a computer.