Convert dds to ngg Online: dds2ngg

You can use Tom's Editor to easily convert images from
Direct Show Surface .DDS to Nokia Group Graphics .NGG.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

DDS

DDS are files invented by Microsoft to be used in games, mostly as textures. Images can be compressed to save space but the compression methods defined by DDS are all very fast in terms of coding and decoding.

NGG

Nokia Group Graphics is an image format with extension NGG.