How to swap colors in an image?

[TheMasterGabriel]

Is there a way to swap the colors of an image? For example, in the image below the white can become the red and the red can become the white. I need the anti-aliasing around the edge of the circle to swap as well.

The circle is just an example. I'm asking more generically, so I can apply the same commands to any image of 2 main colors (and anti-alisasing between them).

[snibgo]

I can't think of an easy way to do this. A hard way is:

1. Get the two most common colours.

2. Convert those with "-level-colors" to black and white, and from there to the original colours in the opposite order.

This should work, including anti-aliasing, but it needs two commands in a script.

[TheMasterGabriel]

Oh wow "-level-colors" is what I was looking for!
I already knew the 2 main colors, so it was as simple as running:

Code: Select all

convert test.png -level-colors "#73233C",white +level-colors white,"#73233C" test_swapped.png

Is there a way to preserve transparent pixels in the image?

[snibgo]

What version IM? "level-colors" doesn't change transparency, for me, using IM v6. For v7, we need to restrict the operations to RGB channels, with "-channel RGB" before the operations and "+channel" after.

Code: Select all

magick test.png -channel RGB -level-colors "#73233C",white +level-colors white,"#73233C" +channel test_swapped.png