I was working on a painting and noticed that for some reason my "black" was washed out. Even setting it to 0,0,0 didn't fix it. I went ahead and exported the image and the export has the black restored to black!
edit: The frog's toes are black
I went back and tried everything, shutoff all but the image layers but nothing seemed to work. Restarting a new picture with the exported layer did work. Is this just some quirk?