TODO - list of things to do for libpng:

* Fix all defects (duh!)
* Better C++ wrapper / full C++ implementation (?)
* Fix the problems with C++ and 'extern "C"'.
* cHRM transformation.
* Palette creation.
* "grayscale->palette" transformation and "palette->grayscale" detection.
* Improved dithering.
* Multi-lingual error and warning message support.
* Complete sRGB transformation.  (Currently it simply uses gamma=0.45455.)
* Man pages for function calls.
* Better documentation.
* Better filter selection
  (e.g., counting huffman bits/precompression; filter inertia; filter costs).
* Histogram creation.
* Text conversion between different code pages (e.g., Latin-1 -> Mac).
* Avoid building gamma tables whenever possible.
* Greater precision in changing to linear gamma for compositing against
  background, and in doing rgb-to-gray transformations.
* Investigate pre-incremented loop counters and other loop constructions.
* Interpolated method of handling interlacing.
* More validations for libpng transformations.