how do i invert a specular map to end up with a normal map

im not sure thats possible, even if it is this isnt the place to ask. you should go to a blender forum or at least a forum that deals with modeling and art. basically your asking how to do something in a program other than unreal, with unreal being the topic of this site id say your a bit off topic.

i want to know how using blender i invert a specular map to end up with a normal map