Black and White Converter

What the Black and White Converter Does

This makes a true black-and-white image — a process called thresholding or binarisation. Unlike grayscale, which keeps 256 shades, this keeps exactly two: black and white. The effect is high-contrast and graphic.

A threshold slider decides the cut-off. Each pixel's brightness is measured, and anything at or above the threshold turns white while anything below turns black. Lower the threshold to keep more white; raise it to push more to black.

How It Works

Drop or pick an image. It is drawn onto a canvas in your browser.

Each pixel's brightness is computed with the luma formula (0.299 red, 0.587 green, 0.114 blue), then compared to the threshold. At or above, the pixel becomes white; below, it becomes black.

Drag the threshold slider to taste, then download. The output is a lossless PNG, and the canvas re-encode strips EXIF and GPS metadata.

Processing pipeline

1. Decode locally. Your image is drawn onto a canvas in the browser — never uploaded.
2. Measure brightness. Each pixel's luma is computed as 0.299 red plus 0.587 green plus 0.114 blue.
3. Threshold to two values. Luma at or above the threshold becomes white (255); below becomes black (0).
4. Export the PNG. The two-colour canvas is saved as a lossless PNG with your original base name.

Threshold to black or white

Every pixel ends as pure black or pure white — only two values. That is what makes this true black and white rather than grayscale, which keeps 256 shades.

Privacy

Your image is processed entirely in your browser and never uploaded — there is no server.

The canvas re-encode strips all EXIF and GPS metadata, so the black-and-white PNG carries no camera or location tags.

No account, no stored copy; everything is gone when you close the tab.

Technical Details

Standards & references

• Thresholding / binarisation — The standard way to turn a grayscale image into two values: pixels below the threshold become black, those at or above become white.
• Two-value (1-bit) image — A true black-and-white image holds only two possible pixel values, unlike grayscale's 256 levels.

Accuracy & Limitations

This is real black and white — exactly two values — not grayscale. If you want shades of gray with detail preserved, use the grayscale converter instead.

The result depends heavily on the threshold. A single fixed cut-off suits high-contrast art and clean scans, but a photo with uneven lighting may lose detail in shadows or highlights; adjust the slider to balance it.

The threshold is global — the same value is applied across the whole image. It does not adapt region by region, so very uneven lighting can give patchy results.

The output is a lossless PNG at the original dimensions. Because there are only two colours, this kind of image compresses extremely well.

Real-World Use Cases

When to use it — and when not to

For shades of gray with detail, use the grayscale converter; to flip colours to their opposite rather than threshold them, use the colour inverter.

Frequently Asked Questions

References

• Thresholding (image processing) — Wikipedia
• Binarize — Wolfram Language
• HTMLCanvasElement: toBlob() (MDN)

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