I am trying to change the background colour of the image https://www.eso.org/public/images/eso0728c/ from black to white with gimp.
To do this I'm following the suggestion from this answer: https://graphicdesign.stackexchange.com/a/11080/130689
The problem now is that all colours get lighter, see the second image below. I'd like the colours to stay the same, just the background should be white, as I tried to draw manually in the 3rd image below.
Any suggestions which technique I could try?