Convert hpm to dds Online: hpm2dds

You can use Tom's Editor to easily convert images from
Grass' Slideshow .HPM to Direct Show Surface .DDS.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

HPM

Grass' Slideshow is an image format with extension HPM.

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.