Colour inversion replaces each channel with its opposite value. It can help create an effect or inspect a dark asset, but it changes the meaning of colours rather than correcting them.
Invert Image Colours applies the PHP negative filter to the decoded image. The operation does not alter the canvas dimensions.
Red becomes cyan
An opaque RGB pixel of 255, 0, 0 becomes 0, 255, 255. Black becomes white and white becomes black. A colourful photograph therefore turns into an unfamiliar palette rather than a normal brightness correction.
The result can make light lettering visible on a different background, but check the edges and any colours that were intended to identify a brand or status.
Inversion is not the same as changing a dark webpage theme. A theme uses separately chosen colours, while a pixel inversion applies its rule to every part of the image.
Do not mistake it for restoration
The tool does not recover a photographic negative with a colour managed film workflow. It performs a general filter operation, without analysing film stock, exposure or an orange mask.
For an application document, reversed text and backgrounds may be unacceptable even when they remain readable. Follow the receiving system's requirements rather than submitting an effect version.
Use PNG if you need to preserve transparent regions. JPEG introduces its own solid background and lossy encoding decisions after the filter.
Keep the source and compare the result in the context where it will be displayed. Inversion can be useful for an intentional design effect, but it should not be described as making the original colours more accurate.