crnlib

This is a port from crunch/crnlib, the license could be found at the end of file

Usage

```rust use std::io::prelude::*; let sample = "samples/test.crn"; let mut file = std::fs::File::open(sample).expect("open sample crn file"); let mut buffer = Vec::new();

let header = Header::parse(&buffer).expect("parse");

let tables = header.gettable(&buffer).expect("read table"); let level0 = header.unpacklevel(&tables, &buffer, 0).expect("unpack");

// level0 contains DXT encoded image content, which could be read by image use image::ImageDecoder; let (width0, height0) = header.getlevelinfo(0).expect("get level info"); let variant = match header.format { Format::Dxt1 => image::dxt::DXTVariant::DXT1, Format::Dxt3 => image::dxt::DXTVariant::DXT3, Format::Dxt5 => image::dxt::DXTVariant::DXT5, format => unimplemented!("image does not support format {:?}", format), }; let decoder = image::dxt::DxtDecoder::new(std::io::Cursor::new(&level0), width0 as u32, height0 as u32, variant).expect("new image"); let mut raw = vec![0; decoder.totalbytes() as usize]; let colortype = decoder.colortype(); decoder.readimage(&mut raw).expect("decode dxt"); let f = std::fs::File::create(std::path::Path::new(sample).withextension("tga")).expect("create sample tga file"); let encoder = image::tga::TgaEncoder::new(f); encoder.encode(&raw, width0 as u32, height0 as u32, colortype).expect("encode tga"); ```

Document of Table

• Any table contains 2 huffman tree
  • 14 bit of maxsymbolcount of second tree
  • "symbol_count" of first temporary tree, the symbol was reordered as [ShortZero, LongZero, ShortRepeat, LongRepeat, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15, 16].
  • temporary one has Key 0..=16 as well as ShortZero, LongZero, ShortRepeat, LongRepeat which come with a parameter with 3, 7, 2, 6 bits.
  • the depth array (of length maxsymbolcount) of second one is encoded using first one.
• A huffman tree is stored using symboldepth.
  • symboldepth means length of code in bits.
  • the Code is assign to Key from small depth to large, then follow the ord of Key.

License of Crunch

``` crunch/crnlib uses a modified ZLIB license. Specifically, it's the same as zlib except that public credits for using the library are required.

Copyright (c) 2010-2016 Richard Geldreich, Jr. All rights reserved.

This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software.

2. If you use this software in a product, this acknowledgment in the product documentation or credits is required:

"Crunch Library Copyright (c) 2010-2016 Richard Geldreich, Jr."

1. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.

2. This notice may not be removed or altered from any source distribution. ```