Convert jpt to dds Online: jpt2dds

You can use Tom's Editor to easily convert images from
JPEG-2000 Code Stream Syntax .JPT to Direct Show Surface .DDS.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

JPT

JPEG-2000 Code Stream Syntax is an image format with extension JPT.

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.