Swap every colour for its opposite, like a photo negative.
Each colour channel is flipped to its opposite: a red value of 0 becomes 255, and 255 becomes 0. White turns black, black turns white, and colours swap for their complements, so blue becomes yellow and green becomes magenta. Inverting the result again gives you back the original exactly. Transparency isn't touched, so a transparent PNG stays transparent.
Scans of black-and-white negatives invert well. Colour negatives have an orange base layer, so a plain inversion leaves a strong blue cast; you'll need to correct the colour afterwards in a photo editor.
Yes. Run the inverted image through the tool again and you get the original colours back.
Not fully. The orange film base leaves a blue tint that needs colour correction afterwards.
It's similar for black text on white, but it also flips colours in photos, which smart dark modes avoid.
Every colour flips to its opposite, so skin turns blue-green and shadows become highlights. That's expected; it's the same look as a film negative.
No. Inversion happens in your browser.
OneClickly is a set of 119 free tools for PDFs, images, text, everyday math and code. They run in your browser, so the files and text you work with stay on your device.