# fdeflate

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A fast and safe deflate implementation for PNG.

This crate contains an optimized implementation of the [deflate algorithm](https://en.wikipedia.org/wiki/Deflate) tuned for PNG images.

At least on PNG data, our decoder rivals the performance of `zlib-ng` and `zlib-rs` without using any `unsafe` code.

When compressing it makes a bunch of simplifying assumptions that
drastically improve encoding speed while still being compatible with zlib:

- Exactly one block per deflate stream.
- No distance codes except for run length encoding of zeros.
- A single fixed huffman tree trained on a large corpus of PNG images.
- All huffman codes are <= 12 bits.

### Inspiration

The algorithms in this crate take inspiration from multiple sources:
* [fpnge](https://github.com/veluca93/fpnge)
* [zune-inflate](https://github.com/etemesi254/zune-image/tree/main/zune-inflate)
* [RealTime Data Compression blog](https://fastcompression.blogspot.com/2015/10/huffman-revisited-part-4-multi-bytes.html)