Convert pgm to dds Online: pgm2dds
You can use Tom's Editor to easily convert images from
Portable aNy Map .PGM to Direct Show Surface
Tom's Editor is a free, online image manipulation and converter program.
Go to Tom's Editor
Portable aNy Map is an image format with extension PGM.
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.