s2tc

Subset of a well-known texture compression scheme

S2TC's format specification is very easy to implement, so it is not hard to make a working compressor or decompressor for it. It is based on Color Cell Compression[1] from 1986, and decoding is done entirely using the methods from there. Encoding is done using a search and refinement method that is derived from the methods described in that paper. This also makes this format a great platform for learning about texture compression and how to tune a compressor for best quality. S2TC is especially well suited for runtime (on-load) compression of textures, as it is - in low quality settings - way faster than any other texture compressors out there.