Is there any way to reuse a texture to make a UV Map in Blender?

[Guest SexualAardvark]

Trying to convert this one dress to BBP, and I don't mind spending the time to make mesh slices... but I got halfway through before I realized that a texture already exists and the map I was making had nothing to do with how it worked. @_@ Is there some simple way I can try to throw the textures on to make a map from that?