libpng is the official
Portable Network Graphics
Portable Network Graphics (PNG, officially pronounced , colloquially pronounced ) is a raster-graphics file format that supports lossless data compression. PNG was developed as an improved, non-patented replacement for Graphics Interchange F ...
(PNG)
reference
Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''name'' ...
library
A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...
(originally called pnglib). It is a platform-independent library that contains
C functions for handling PNG images. It supports almost all of PNG's features, is extensible, and has been widely used and tested for over 23 years.
libpng is dependent on
zlib
zlib ( or "zeta-lib", ) is a software library used for data compression. zlib was written by Jean-loup Gailly and Mark Adler and is an abstraction of the DEFLATE compression algorithm used in their gzip file compression program. zlib is also ...
for data compression and decompression routines.
libpng is released under the
libpng license
The zlib license is a permissive free software license which defines the terms under which the zlib software library can be distributed. It is also used by many other free software packages. The libpng library uses a similar license sometimes r ...
, a
permissive free software licence
A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, ...
, and is
free software
Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...
. It is frequently used in both
free and