StandardPNG

StandardPNG is a term used in software development and digital imaging to describe a proposed baseline for using the Portable Network Graphics format in a way that maximizes interoperability, performance, and accessibility. It is not an official standard recognized by a formal standards body; rather, it conveys a set of informal guidelines that various projects adopt.

Goals and scope: StandardPNG emphasizes valid PNG encoding, broad compatibility across tools and viewers, and predictable rendering. Typical recommendations include using truecolor with alpha (RGBA) at 8 bits per channel, adopting the sRGB color space, minimizing nonessential metadata, and avoiding application-specific or opaque chunks that may hinder portability. It also encourages using lossless DEFLATE compression with sensible settings to balance file size and rendering performance.

Technical considerations: PNG files have a chunk-based structure, beginning with an 8-byte signature and containing critical chunks such as IHDR, IDAT, and IEND, along with optional chunks like PLTE, tRNS, gAMA, iTXt, and iCCP. A StandardPNG guideline would generally require the file to be a valid PNG that conforms to these rules, and would advise avoiding unnecessary or proprietary chunks to ensure compatibility. Interlacing with Adam7 is permitted but often discouraged for web usage to simplify progressive rendering.

Adoption and status: Because StandardPNG is informal, there is no official certification or governing body enforcing it. It is used by developers and content pipelines to describe a conventional PNG usage pattern. By contrast, the formal PNG specification is maintained by the PNG Development Group and has broad industry acceptance.