Convert j2k to dds Online: j2k2dds
You can use Tom's Editor to easily convert images from
JPEG-2000 Code Stream Syntax .J2K to Direct Show Surface
Tom's Editor is a free, online image manipulation and converter program.
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JPEG-2000 Code Stream Syntax is an image format with extension J2K.
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.