BYTETOOLS

Image Threshold

Convert an image to pure black and white with an adjustable luminance threshold. Free, private, browser-based binarize tool with live preview.

Drop an image to thresholdProcessed locally — never uploaded

What is the Image Threshold?

The ByteTools Threshold tool converts an image to pure black and white — no grays. Each pixel becomes either black or white depending on whether its brightness is above or below the threshold you set, a process known as binarization.

  • Pure black-and-white (binary) output
  • Adjustable luminance threshold from 0 to 255
  • Luminance-weighted brightness for natural results
  • Great for documents, stencils and line art
  • Fast single-pass processing with live preview
  • 100% private — images never leave your browser

How to use the Image Threshold

  1. 1

    Drop an image into the upload area, or click to browse.

  2. 2

    Drag the threshold slider between 0 and 255.

  3. 3

    Watch pixels flip to pure black or white in the live preview.

  4. 4

    Click Download PNG to save the black-and-white image.

About the Image Threshold

The ByteTools Threshold tool converts an image to pure black and white — no grays. Each pixel becomes either black or white depending on whether its brightness is above or below the threshold you set, a process known as binarization.

Slide the threshold to control how much of the image turns black versus white. It is useful for scanning documents to clean high-contrast text, preparing line art, creating stencils, or producing a bold graphic look from a photo.

The conversion runs locally on an HTML canvas in your browser using a single pass over the pixels. Your image is never uploaded, so scanned documents and private pictures stay on your device.

Frequently asked questions

How do I convert an image to pure black and white?

Upload the image and drag the threshold slider until the balance of black and white looks right, then download the PNG. Every pixel becomes either black or white with no gray in between.

What is image thresholding?

Thresholding, or binarization, compares each pixel's brightness to a cutoff value. Pixels brighter than the cutoff turn white and darker ones turn black, producing a two-tone image often used for documents and line art.

How is threshold different from grayscale?

Grayscale keeps a full range of gray tones, while thresholding removes all grays and leaves only pure black and white. Threshold gives a much higher-contrast, graphic result.

Is my image uploaded when I threshold it?

No. The black-and-white conversion is done in your browser with the canvas API, so nothing is sent to a server and your files remain private.

Guides for Image Threshold

Related tools