Definition compressionBlockSizeX (c : compressionMethod) : nat :=
  match c with
  | CompressionUncompressed       => 0
  | CompressionBC1                => 4
  | CompressionBC2                => 4
  | CompressionBC3                => 4
  | CompressionBC4                => 4
  | CompressionBC5                => 4
  | CompressionBC6                => 4
  | CompressionBC7                => 4
  | CompressionETC1               => 4
  | CompressionETC2               => 4
  | CompressionEAC                => 4
  | CompressionASTC x _           => x
  | CompressionCustom _ x _ _ _ _ => x
  end.
