Sunday, March 1, 2026

.ASTC (the File Format): No Longer a Black Box

The basisu command line tool has a new option, -peek, which opens any standard ARM LDR/HDR .ASTC texture file, unpacks each block, and computes a bunch of statistics about the exact ASTC configurations the blocks used.

This is how we found out that Intel's ispc_texcomp's ASTC encoder is, for all practical purposes, broken.

https://github.com/BinomialLLC/basis_universal/wiki/Displaying-.astc-file-block-statistics-using-the-peek-command-line-option