I want to match the appearance of an image that is partly transparent. The problem is that I cannot obtain the original image. I can only obtain screenshots of it against different backgrounds.
Using images of it against black and white backgrounds, is there a way to derive the original image? Ideally, I'd like to derive the non-transparent version of it, along with its transparency level. I want to edit it, then re-apply the transparency.
I'm working with GIMP 2.6 on Linux, but I could obtain other software as needed.