AwesomeBump (AKA: Awesome Bump) is a free and open-source alternative of CrazyBump or the Insane Bump plugin for GIMP, developed by Krzysztof Kolasinski from Poland, using Qt library. It is used to generate high-quality normal, height, specular or ambient occlusion, metallic, roughness and other textures from a single image.

Bitmap2Material (B2M for short, the predecessor of Substance Alchemist) is a powerful and easy-to-use free tool that helps game developers quickly generate a full set of seamless textures (normal map, height map, highlight map, etc.) from a single bitmap format of image, developed by Allegorithmic (also the developer of Substance suite) from France, which was acquired by Adobe in 2019.

Materialize is an amazing free image to material conversion tool, developed by Bounding Box Software. It can quickly and easily generate high-quality tileable 3D materials for use in game development. With it, you can create an entire material from a single image or import the texture map you have and generate any other texture map you need.

CrazyBump is simple, easy-to-use yet professional 2D photo-to-3D map generation application. It doesn't offer many adjustable parameters, but still has a lot more details than the functionally similar Photoshop plugins, and is much easier to operate. Plus, it supports exporting normals, displacement, occlusion, specularity, and diffuse these five types of maps at the same time (i.e.: importing one image will result in five effects of maps simultaneously), as well as real-time preview.