Image Grayscale

Quick answer: Convert images to black-and-white grayscale — for scans, prints, and OCR prep. Open 图片灰度转换 — everything runs locally in your browser, and files never leave your device.

Steps

1. Upload the image to the Grayscale tool.
2. Preview and optionally tune contrast.
3. Download.

Important notes

• Grayscale conversion is one-way — keep the color original.
• Grayscale + higher contrast before OCR often improves recognition on tinted paper.

Common questions

Is it just desaturation? It uses luminance weighting, which matches perceived brightness better than dropping one channel.

Batch? Yes.

When to use this

Grayscale is also the go-to preprocessing for photocopy-style documents and cheaper black-and-white printing; pair it with a small contrast lift for crisper text.

Pro tips

Grayscale conversion quality depends on what happens after the color drop: plain desaturation leaves flat contrast, so nudge contrast up 5-10% to restore punch. For OCR preprocessing, the opposite applies — aim for maximum text/background separation, which often means higher contrast and a slight brightness lift on yellowed paper. Keep the color original always: several printers and print shops interpret grayscale files differently, and you may need to re-derive the grayscale with different settings without re-scanning.

Does grayscale reduce file size? Often yes for JPEGs (fewer color channels to describe), though heavily compressed color originals may shrink less than expected.