png

png is a pure-Rust library for decoding and encoding PNG images, including animated PNG (APNG). It contains no unsafe code, is continuously fuzzed on OSS-Fuzz, and delivers performance typically on par with or better than libpng.

The crate powers the wider image-rs ecosystem and ships a fast encoding mode built on fdeflate that beats libpng’s fastest mode while producing better compression ratios. It exposes a streaming Decoder and Encoder API for reading and writing PNG data with full control over color types, bit depth, filtering, and metadata.

What You Get

• A streaming PNG Decoder that reads images incrementally
• A configurable Encoder with color type, bit depth, and filter control
• Animated PNG (APNG) decoding and encoding support
• A fast fdeflate-powered encoding mode faster than libpng
• Text and metadata chunk handling plus sRGB support

Common Use Cases

• Loading PNG images into applications and image pipelines
• Encoding rendered or processed pixel data to PNG files
• Reading and writing animated APNG sequences
• Extracting or embedding PNG text metadata and color profiles

Under The Hood

Architecture - The crate splits cleanly into a decoder module (src/decoder) that parses PNG chunks incrementally and an encoder.rs that writes them, with a filter module implementing the PNG scanline filters and adam7.rs handling interlacing. Shared code lives in chunk.rs, common.rs, and traits.rs, while text_metadata.rs and srgb.rs handle ancillary chunks. Compression is delegated to the deflate crates rather than reimplemented.

Tech Stack - Pure Rust (2021 edition, rust-version 1.73) with no unsafe code. It depends on fdeflate for fast deflate encoding, flate2 and miniz_oxide (with SIMD) for compression, crc32fast for chunk checksums, and bitflags for option handling. An optional unstable feature enables extra decode speedups on nightly.

Code Quality - The project is battle-tested and continuously fuzzed on OSS-Fuzz, with a fuzz/ harness, a png-afl target, a tests/ suite, and benches/ for performance tracking. CI runs via GitHub Actions. The absence of unsafe code plus fuzzing gives strong confidence in its robustness against malformed input.

API Design - The Decoder/Encoder API is straightforward: construct a Decoder over any Reader, obtain frame info, and read rows into a buffer; encoding mirrors this with a builder-style Encoder. docs.rs documentation and examples cover common flows, though full control over PNG’s many color types, bit depths, and filter strategies exposes the format’s inherent complexity.