texgenpack
Texture compression and conversion program with KTX and DDS support.
...The image format supported is PNG, while for textures there is support for KTX, PKM and DDS using ETC1, ETC2, DXT1/3/5 or BPTC (BC7) texture compression. Several uncompressed texture format are also supported.
This program requires the installation of libfgen, also avalable on SourceForge.