Crate ctt_etcpak 

Safe Rust bindings to etcpak — an extremely fast ETC/EAC/BC texture compressor and decompressor.

ISA dispatch

etcpak uses compile-time SIMD ISA selection. This crate compiles multiple variants and selects the best one at runtime:

• x86_64: SSE4.1 and AVX2 variants (selected via std::is_x86_feature_detected!)
• aarch64: NEON (the only variant, always available on AArch64)

Pixel format

All compression functions expect 4 bytes per pixel, packed as uint32_t. The channel ordering within each pixel depends on the codec:

• ETC1/ETC2/EAC codecs: B8 G8 R8 A8 (BGRA — blue in lowest byte)
• BC codecs: R8 G8 B8 A8 (RGBA — red in lowest byte)

Input data must be tightly packed (stride = width × 4 bytes).

Decompression functions output uint32_t per pixel in native etcpak layout.

Modules

bc1

BC1 (DXT1) block compression — RGB with optional 1-bit alpha.

bc3

BC3 (DXT5) block compression — RGBA.

bc4

BC4 block compression — single channel (red).

bc5

BC5 block compression — dual channel (red + green, typically normals).

decode

Decompression functions for all supported formats.

eac_r

EAC R11 block compression — single channel (red).

eac_rg

EAC RG11 block compression — dual channel (red + green).

etc1

ETC1 block compression — RGB, no alpha.

etc2_rgb

ETC2 RGB block compression — RGB, no alpha.

etc2_rgba

ETC2 RGBA block compression — RGB with alpha.

Structs

Surface

Describes a 2D image for compression.

Functions

output_size_64bpb

Output size for formats using 64-bit (8-byte) blocks: ETC1, ETC2 RGB, EAC R, BC1, BC4.

output_size_128bpb

Output size for formats using 128-bit (16-byte) blocks: ETC2 RGBA, EAC RG, BC3, BC5.