The PNG Reference Library documentation—traditionally known as the official libpng manual—serves as the definitive guide for implementing, reading, and writing Portable Network Graphics (PNG) files. It is widely paired with Greg Roelofs’ historic book, PNG: The Definitive Guide, which provides the foundational theory and practical usage of the reference library. Key Pillars of the Reference Documentation
The guide outlines how to handle the C-based library through several critical pillars:
Core Structures: Manages data flow via png_struct (internal library execution state) and png_info (image metadata details).
Signature Verification: Validates files using png_sig_cmp() to safely check the initial 1 to 8 bytes against the official PNG header.
Sequential Reading: Walks developers through png_read_info(), image transformations, and row-by-row pixel retrieval.
Data Decompression: Integrates directly with the zlib library to manage lossless layout compression.
Custom Implementations: Details memory allocation overrides and custom error handlers using png_set_error_fn. Core Technical Sections
The official technical guide is traditionally divided into five key functional categories: PNG Documentation – libpng.org
PNG Specification (versions 1.0 through 1.2 and ISO/IEC/W3C), Extensions, and Register: US (California) or local mirror site. US ( libpng.org
PNG: The Definitive Guide | Guide books – ACM Digital Library
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