PNG optimization library
OPNGLIB is the PNG optimization library used by optipng.It consists of the following components:
Copyright (C) 2001-2011 Cosmin Truta.
This software is distributed under the zlib license. Please see the accompanying LICENSE file, or visit http://www.opensource.org/licenses/zlib-license.php
OPNGLIB is not thread-safe: it is currently not possible to create two or more optimizer objects in a process.