texture2ddecoder

A pure Rust no-std texture decoder for the following formats:

• ATC - Adreno Texture Compression (detailed paper)
• ASTC - Adaptive Scalable Texture Compression
• BCn - Block Compression
• ETC - Ericsson Texture Compression
• PVRTC - PowerVR Texture Compression

and with alloc:

• Crunch & Unity's Crunch (unity branch)

Features

alloc (optional, default)

• ~35% faster pvrtc decoding
• crunch decoding

Functions

Provides a decode function for each format, as well as a block decode function all formats besides PVRTC. Besides some exceptions, the signature of the decode functions is as follows:

    fn decode_format(data: &[u8], width: usize, height: usize, image: &mut [u32]) -> Result<(), &'static str>
    // data: the compressed data, expected to be width * height / block_size in size
    // width: the width of the image
    // height: the height of the image
    // image: the buffer to write the decoded image to, expected to be width * height in size
    fn decode_format_block(data: &[u8], outbuf: &mut [u32]) -> Result<(), &'static str>
    // data: the compressed data (block), expected to be block_size in size
    // outbuf: the buffer to write the decoded image to, expected to be block_size in size

The exceptions are:

• ASTC: the (block) decode function takes the block size as an additional parameter
• BC6: there are two additional decode functions for the signed and unsigned variants
• PVRTC: the decode function takes the block size as an additional parameter, and there are two additional decode functions for the 2bpp and 4bpp variants
• Crunch & Unity's Crunch: The texture's dimensions and metadata are stored in the file itself, the header must be parsed with crnd_get_texture_info() from CrnTextureInfo struct first, then pass the metadata to the decoder. There's no block decompression function.

Here is a list of the formats and their corresponding functions:

• ATC
  • decode_atc_rgb4
  • decode_atc_rgb4_block
  • decode_atc_rgba8
  • decode_atc_rgba8_block
• ASTC
  • decode_astc
  • decode_astc_block
  • various decode_astc_(block_)_x_y functions, where x and y are the block size
• BCn
  • decode_bc1
  • decode_bc1_block
  • decode_bc3
  • decode_bc3_block
  • decode_bc4
  • decode_bc4_block
  • decode_bc5
  • decode_bc5_block
  • decode_bc6
  • decode_bc6_block
  • decode_bc6_signed
  • decode_bc6_block_signed
  • decode_bc6_unsigned
  • decode_bc6_block_unsigned
  • decode_bc7
  • decode_bc7_block
• ETC
  • decode_etc1
  • decode_etc1_block
  • decode_etc2_rgb
  • decode_etc2_rgb_block
  • decode_etc2_rgba1
  • decode_etc2_rgba1_block
  • decode_etc2_rgba8
  • decode_etc2_rgba8_block
  • decode_eacr
  • decode_eacr_block
  • decode_eacr_signed
  • decode_eacr_signed_block
  • decode_eacrg
  • decode_eacrg_block
• PVRTC
  • decode_pvrtc
  • decode_pvrtc_2bpp
  • decode_pvrtc_4bpp
• Crunch
  • decode_crunch
• Unity Crunch
  • decode_unity_crunch

Roadmap

• documentation
• replacing u32 color output with RGBA structure
• finding the original sources for the decoders
• supporting more than BGRA32 output
• adding additional formats

Format Progress

• ATC-RGB
• ATC-RGBA
• ASTC
• BC1
• BC3
• BC4
• BC5
• BC6
• BC7
• EAC-R
• EAC-RG
• ETC1
• ETC2
• ETC2-A1
• ETC2-A8
• PVRTCI-2bpp
• PVRTCI-4bpp
• Crunched
  • DXT1
  • DXT5
  • ETC1
  • ETC2-A8

License & Credits

This crate itself is dual-licensed under MIT + Apache2.

The texture compression codecs themselves have following licenses:

Codec	License	Source
ATC	MIT	Perfare/AssetStudio - Texture2DDecoderNative/atc.cpp
ASTC	MIT*	Ishotihadus/mikunyan - ext/decoders/native/astc.c
BCn	MIT*	Perfare/AssetStudio - Texture2DDecoderNative/bcn.cpp
ETC	MIT*	Ishotihadus/mikunyan - ext/decoders/native/etc.c
f16	MIT	Maratyszcza/FP16
PVRTC	MIT*	Ishotihadus/mikunyan - ext/decoders/native/pvrtc.c
Crunch	PUBLIC DOMAIN	BinomialLLC/crunch
Crunch (Unity)	ZLIB	Unity-Technologies/crunch
* in doubt if these are the original source and have not just taken/adopted the code from somewhere else