Texture creation tool for unity
Download or clone the repository and copie the files into your Asset folder. The tool is then found under Window->TextureCreator.
You can select an image into the Load panel. I keep my source images into a folder, they can have any size. The value of the different panel parameters are saved automatically for each source image into Assets/TextureCreator/Save/. These can be deleted at any point if not needed.
For each panel the texture can be written to disk using the write button at the top. The textures are saved into Assets/Textures/. If a material has been created in the Load panel, textures will be automatically assigned to it.
See this video for some examples: