Gera Tools

Invert Image Colours Online

Create a photographic negative of any image with adjustable strength.

Free tool to invert image colours online. Upload an image and turn it into a photographic negative — each colour channel replaced by 255 minus its value — with an adjustable strength slider, then download the PNG. Runs in your browser; nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Last updated Source: Gera Tools

How is a colour inverted?

Each of the red, green and blue channels is replaced by 255 minus its value, so black becomes white, red becomes cyan, and so on. This produces a true photographic negative. The strength slider linearly blends between the original and the full inversion.

Inverting an image swaps every colour for its opposite, turning it into a photographic negative. Upload an image, choose how strongly to apply the effect, and download the result.

The maths

For each pixel, every colour channel is flipped:

newValue = oldValue + (255 - 2 × oldValue) × strength

At 100% strength this reduces to 255 - oldValue — a full inversion where black becomes white and each colour becomes its complementary hue. At lower strengths the image blends toward mid-grey, which can create a faded, washed-out look.

Notes

  • Only the colour channels are inverted; the alpha channel is left alone, so transparency is preserved.
  • The export is a lossless PNG.
  • Everything runs locally in your browser — the image is never uploaded.

Inversion is handy for previewing a dark-mode version of a diagram, creating negative-film effects, or checking how an image reads with its tones reversed.