Mipmapping describes the level of detail that is a necessary consideration in terms of presenting your scene. A mipmap is a sequence of textures, each of which is a progressively lower resolution representation of the same image. Mipmapping improves the quality of rendered textures at the expense of using more memory. When saving a file in the DDS format with the help of ImageConverter Plus (when the “Generate mip maps” option is selected) mipmaps are additional texture map sizes that are created. But you should note that to use the DDS format successfully with mipmap levels option, the size of the image you are saving should be equal to a power of two (128, 512, 1024 etc.). To fulfill this requirement, you can try various operations: crop, resize , canvas.