OptiPNG - TO-DO list
====================

- Compression improvements:
  Use zlib's deflateTune().
  Use 7zip's powerful deflation engine.
  (This is not possible with libpng, so a custom encoder is needed.)

- Speed improvements:
  Avoid repeated filtering when trying a filter value more than once.
  (This is not possible with libpng, so a custom encoder is needed.)

- Text chunk optimization:
  Smart selection between tEXt and zTXt.  Similarly for iTXt.

- More file recovery features.

- Input from stdin; output to stdout.

- Optimization of an entire directory, with and without subdirectory
  recursion:
    optipng dir/
    optipng -recurse dir/

- Improved support for reading external image formats
  (e.g. compressed TIFF).

- Support for conversion to a desired bit depth and color type:
    optipng -b16 -c6 ...

- Support for handling metadata, e.g.:
    optipng -set tEXt=<keyword>,<text>     # add or update chunk
    optipng -set sRGB=0                    # add or update chunk
    optipng -set image.precision=<n>       # set the precision of all samples
    optipng -set image.alpha.precision=<n> # set the precision of alpha samples
    optipng -reset image.alpha             # make the image fully opaque
    optipng -strip hIST,sPLT               # strip hIST and sPLT
    optipng -strip all -protect iCCP       # strip all metadata except iCCP

- Parallelization on multi-processor/multi-core machines.

- A shared library (e.g. optipng.dll), to facilitate the development of
  PNG-optimizing GUI applications and plugins.