Astc-encoder-py

The 2.1 release is the second release in the 2.x series. It includes another set of significant performance optimizations and number of smaller new features.

:warning: A reminder for users of the library interface - the library API is not designed to be stable across versions, and this release is not compatible with 2.0. Please recompile the client-side using the updated `astcenc.h` header.

Features:

* **Command line:**
* **Bug fix:** The meaning of the `-tH\cH\dH` and `-th\ch\dh` compression modes was inverted. They now match the documentation; use `-*H` for HDR RGBA, and `-*h` for HDR RGB with LDR alpha.
* **Feature:** A new `-fastest` quality preset is now available. This is designed for fast "roughing out" of new content, and sacrifices significant image quality compared to `-fast`. We do not recommend its use for production builds.
* **Feature:** A new `-candidatelimit` compression tuning option is now available. This is a power-user control to determine how many candidates are returned for each block mode encoding trial. This feature is used automatically by the search presets; see `-help` for details.
* **Improvement:** The compression test modes (`-tl\ts\th\tH`) now emit a MTex/s performance metric, in addition to coding time.
* **Core API:**
* **Feature:** A new quality preset `ASTCENC_PRE_FASTEST` is available. See `-fastest` above for details.
* **Feature:** A new tuning option `tune_candidate_limit` is available in the config structure. See `-candidatelimit` above for details.
* **Feature:** Image input/output can now use `ASTCENC_TYPE_F32` data types.
* **Stability:**
* **Feature:** The SSE2, SSE4.2, and AVX2 variants now produce identical compressed output when run on the same CPU when compiled with the preprocessor define `ASTCENC_ISA_INVARIANCE=1`. For Make builds this can be set on the command line by setting `ISA_INV=1`. ISA invariance is off by default; it reduces performance by 1-3%.

Performance

Performance benefits vary based on image color format, ASTC quality settings, and ASTC block size.

* Compressing using `-thorough` is between 1.3x and 1.6x faster than asctenc 2.0.
* Compressing using `-medium` is between 1.4x and 2.1x faster than asctenc 2.0.
* Compressing using `-fast` is between 1.4x and 2.4x faster than asctenc 2.0.
* Compressing using the new `-fastest` setting is 2.1x - 3.8x faster than using astcenc 2.0 `-fast`.

This is first release of the astcenc 2.x series, providing a number of major improvements for content creators.

The core codec performance is now up to three times faster, with optimized builds for the SSE2, SSE4.2, and AVX2 instruction sets.

The core codec now has a clean library API separating the command line wrapper and the main algorithm core. This makes it easier to directly integrate the compressor into other applications.

The command line tool supports a wider range of input and output file formats for both uncompressed files and compressed files.

**Note: this release is not command line compatible with the 1.x series. Some options have been renamed and some options have been removed.**

* Re-enable JPEG and GIF image support

Update all binaries to source version 62fadfc.