libpngpf (3) - Linux Manuals
libpngpf: Portable Network Graphics (PNG) Reference Library 1.5.13
NAMElibpng - Portable Network Graphics (PNG) Reference Library 1.5.13 (private functions)
As of libpng version 1.5.1, this section is no longer maintained, now that
the private function prototypes are hidden in pngpriv.h and not accessible
to applications. Look in pngpriv.h for the prototypes and a short description
of each function.
DESCRIPTIONThe functions previously listed here are used privately by libpng and are not recommended for use by applications. They are not "exported" to applications using shared libraries.