Convert dds to raw Online: dds2raw
You can use Tom's Editor to easily convert images from
Direct Show Surface
.DDS to RAW Dump
Tom's Editor is a free, online image manipulation and converter program.
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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.
This is just raw pixels saved in a file. Format used mostly by old games. RAW files do not have any header so if you don't know what is the original width and height of the image it might be hard to decode them.