http://github.com/kmkolasinski/AwesomeBump
AwesomeBump is a free and open source program designed to generate normal, height, specular or ambient occlusion, roughness and metallic textures from a single image. Since the image processing is done in 99% on GPU the program runs very fast and all the parameters can be changed in real time. AB was made to be a new alternative to known gimp plugin called Insane Bump. Since version 3.0 AB is supporting PBR shading model which makes this software more Awesome!