Grayscale for photos, pure black and white for paperwork
Two effects in one tool. Grayscale converts colours to matching shades of grey using the same brightness weights as a TV picture, so skin tones and skies look natural. Black & white goes further: every pixel becomes either black or white, decided by a threshold you can move. That second mode is what you want for signatures, stamps, handwritten notes and phone photos of documents – it removes grey paper, shadows and colour casts.
Cleaning up a signature for a form
- Photograph the signature. Sign in black or dark blue ink on plain white paper. Shoot in daylight, straight on.
- Choose “Black & white”. Then move the threshold: lower until the paper is pure white, higher if the ink breaks up.
- Convert to JPG or PNG. Then size it for the form with resize in cm (for example 6 × 2 cm) and a KB limit.
When to use which
- Grayscale
- Portraits, artistic photos, printing a colour picture on a mono printer.
- Black & white
- Signatures, scanned text, line drawings, stamps, preparing images for laser engraving or embroidery.
- Negative
- Inverting scanned film negatives – see the negative image converter.
Frequently asked questions
What is the difference between grayscale and black and white?
Grayscale keeps all shades of grey, like a black-and-white photograph. Pure black and white has only two colours, which makes scanned text and signatures crisper and files much smaller.
How do I clean up a signature photo?
Choose “Black & white” and lower the threshold until the paper turns fully white while the ink stays solid. Save as PNG for the cleanest edges, or JPG if the form requires it.
Will the file get smaller?
Usually. Pure black-and-white PNGs are very small; grayscale JPGs are slightly smaller than colour ones.
Is the photo file uploaded?
No. The image is read and converted by your browser on your own device. Nothing is sent to a server, and nothing is stored.
Can I convert several photo files at once?
Yes. Add as many as you like; each becomes a black-and-white image, and they download together as a ZIP.
Is there a size or daily limit?
No limits and no watermark. Very large images (over about 50 megapixels) may be slow on older phones because the work happens on your device.