Invert Image Colours

What inverting does

Inversion maps every pixel value to its opposite, so black becomes white, white becomes black, and a mid grey stays roughly mid grey. Red becomes cyan, green becomes magenta, and blue becomes yellow, because those are the complementary colours. The result looks like a photographic negative, and it is a completely reversible mathematical operation: inverting the inverted image returns the original exactly, with no quality loss at all.

NoteInversion is fully reversible and loses no data. Inverting twice returns the original exactly.

The one real diagnostic use

There is a genuine technical reason to invert an image, and it comes from film scanning. A photographic negative is darkest where the original scene was brightest, and to make a digital scan resemble the positive photograph it has to be inverted. So inverting a raw film scan, with the correct black and white points applied, is how a film photograph is reproduced digitally. That is a real workflow rather than a novelty, and it is the reason the operation exists at all.

• Film scanning: a negative scan is inverted to reproduce the positive photograph.
• The black and white points must be set before inversion.
• Applying the points after inversion gives an incorrect result.
• This is the original purpose of the operation and the only serious one.

Everything else is novelty or a colour filter

Used on an ordinary photograph, inverting is a creative effect. As a whole-image inversion it is rarely usable beyond a moment, because skin tones turn blue green and the result is immediately strange. Inverted luminance, which keeps the tones but produces a negative of the brightness rather than the colour, is a more plausible filter because it avoids the colour problem. That is the version worth reaching for if the goal is a stylised look rather than a demonstration.

• Whole image inversion: a novelty, and skin tones become unnatural.
• Inverted luminance: keeps the colour, inverts the brightness. More usable.
• Inverted grayscale: produces a photographic negative look.
• For a stylised result, inverted luminance usually beats full inversion.

Accessibility and the inverted interface

Inverted colour is a genuine accessibility mode on operating systems, and a photo that is already high contrast can become genuinely hard to read when inverted. Light text on a dark background inverts to dark text on a light background, which in an image is visually jarring and can be painful for someone who has this mode enabled. That is a real reason to avoid inverting screenshots, diagrams, and anything with text, and it is worth knowing that the person viewing the image may be seeing it through a mode you have not accounted for.

• Inverted interfaces are a real accessibility mode on phones and computers.
• An inverted screenshot becomes painful to read for those users.
• A photo with text inverted is hard to read even for others.
• Avoid inverting screenshots, diagrams, and anything with text on it.