Grayscale image converter

Turn color photos into grayscale (what most people call a black and white photo), many at once, and fine-tune brightness and contrast. Download each image or all of them as a ZIP. Free, no watermark, and your files never leave your browser.

Images (you can pick several)

No images yet. You can also drop files on this box.

Effect

Effect
Method
Style
Strength

Auto threshold Threshold

Brightness 0
Contrast 0

Changes apply to every image instantly.

Output

Format
Quality

For black and white, PNG gives the smallest file and the cleanest edges.

Why not just average the colors?

Our eyes are far more sensitive to green than to blue, so a plain (R+G+B)/3 average makes blue skies look too bright and green leaves too dark. This tool weights the channels the way screens are calibrated (21% red, 72% green, 7% blue, the Rec. 709 luma used for sRGB), so a grayscale photo keeps the brightness you saw in color. Pick Average under Method if you need the plain mean for a specific workflow.

How it works

Each image is decoded by your browser and drawn on a canvas, then every pixel is recalculated in JavaScript: brightness and contrast first, then the effect. Width, height and transparency stay the same (JPG has no transparency, so transparent areas become white). Nothing is uploaded, so it works for private photos and even offline once the page has loaded. EXIF metadata (camera, GPS location) is removed.

Other effects: black and white image converter, invert image colors, sepia filter. To change the shape or size too, use crop image, resize image or rotate image. For a whole PDF, use grayscale PDF.

Screenshots of web pages from code

Converting website screenshots for a print handout or a report? The Shotmint API renders any URL in Chromium and returns a PNG, JPG, WebP or PDF, so you can capture pages in bulk and run the images through this page:

curl "https://shotmint.creasework.com/v1/screenshot?url=https://example.com&width=1280&full_page=true" -H "X-API-Key: YOUR_KEY" -o page.png

Each screenshot or PDF is 1 credit. €5 buys 2,000 with no subscription, and credits never expire.

Get 25 free renders a month Try a website screenshot

FAQ

Are my images uploaded? No. Everything runs in JavaScript on this page.

Does it lose quality? PNG output is lossless. JPG and WebP are re-encoded at the quality you pick. The size in pixels never changes.

Can I undo it? Your original files are untouched; this page only creates new copies. Switch the effect to None to compare, or Reset to start over.

Is there a limit? No file count limit and no watermark. Animated GIF and WebP files are processed as their first frame.