Nominom

Add option to recalculate blue channel for prenormalized bc5 normals

2

B = sqrt(1 - (sqrt(R) + sqrt(G)))

http://richg42.blogspot.com/2021/02/rdo-bc1-bc7-progress.html?m=1 http://richg42.blogspot.com/2021/02/tricks-to-help-reduce-bc7s-output.html?m=1 http://richg42.blogspot.com/2021/02/the-two-types-of-rdo-bc7-encoders.html?m=1

Add support for ETC1S. https://www.khronos.org/registry/DataFormat/specs/1.1/dataformat.1.1.html#ETC1

Add support for UASTC: https://github.com/BinomialLLC/basis_universal/wiki/UASTC-Texture-Specification

Encode a few blocks with same endpoint colors (and indices?) to make them more compressible with lzma/deflate and such.

There's a lot of code-duplication on the public and internal API's. This can probably be reduced by quite a lot.

This project is mostly about block-compressed formats, so including the HdrImage-class was a band-aid fix to allow usage with any kind of a HDR-format. Ideally ImageSharp would implement HDRsupport or...