n function interface to call
<a href="http://www.libpng.org/pub/png/libpng.html">libpng</a>, the
official PNG reference library.  As a result, it benefits from all the
effort that has been put into that library: CL-PNG is much faster than
before, and better able to handle corner cases.

<p>The interface is likely to change in future versions.  Please <a
  href="http://www.ljosa.com/~ljosa/contact">report</a> on your
  experience with the current interface.

<p>The current version has the following limitatio