CPNG is a fork of the PNG image format that aims to modernize it while maintaining backwards compatibility. The 30-year-old PNG format is outdated and lacks new features. By finding a way to add new features without breaking compatibility, CPNG can be used across all browsers, operating systems, and engines. Some of the key features of CPNG include faster encoding/decoding, SIMD encoding, multithreading, and support for real HDR pixels. CPNG also introduces a constrained Deflate feature for encoding speedups. Additionally, CPNG supports FP16 and LOGLUV32 formats for HDR image support. The goal is to make CPNG a true HDR alternative to .EXR with a lossless tone mapped fallback. Though other “HDR” solutions for PNG exist, they often require storing 16-bit pixels even if only a fraction of those bits are actually used. CPNG aims to avoid this unnecessary file size bloat. The author is still working on the LOGLUV32 feature and collaborating with another library author to support half float PNGs. Ultimately, the library authors have control over the format as long as it remains backwards compatible.
https://richg42.blogspot.com/2023/12/announcing-cpng-compatible-network.html