todo

一个国人自己实现图像库的程序（有参考价值）

TODO - list of things to do for libpng:

Final bug fixes.
Improve API by hiding the png_struct and png_info structs.
Finish work on the no-floating-point version (including gamma compensation)
Better C++ wrapper/full C++ implementation?
Fix problem with C++ and EXTERN "C".
cHRM transformation.
Improve setjmp/longjmp usage or remove it in favor of returning error codes.
Add "grayscale->palette" transformation and "palette->grayscale" detection.
Improved dithering.
Multi-lingual error and warning message support.
Complete sRGB transformation (presently it simply uses gamma=0.45455).
Man pages for function calls.
Better documentation.
Better filter selection
   (counting huffman bits/precompression?  filter inertia?  filter costs?).
Histogram creation.
Text conversion between different code pages (Latin-1 -> Mac and DOS).
Should we always malloc 2^bit_depth PLTE/tRNS/hIST entries for safety?
Build gamma tables using fixed point (and do away with floating point entirely).
Use greater precision when changing to linear gamma for compositing against
  background and doing rgb-to-gray transformation.
Investigate pre-incremented loop counters and other loop constructions.