OptiPNG 0.4.5: Advanced PNG optimizer.
Copyright (C) 2001-2004 Cosmin Truta.

This program is open-source software. See LICENSE for more details.
Compiled with libpng version 1.0.15-cos2 and zlib version 1.2.1.f-cos2

Usage:
    optipng [options] files.png ...
Basic options:
    -h, -help		show this help
    -v			verbose mode / show copyright, version and build info
    -o  <level>		optimization level (0-7)		default 2
    -i  <type>		interlace type (0-1)			default <input>
    -k, -keep		keep a backup of the input files
    -log		log messages to "optipng.log"
    -q, -quiet		quiet mode
Advanced options:
    -zc <levels>	zlib compression levels (1-9)		default 9
    -zm <levels>	zlib memory levels (1-9)		default 8
    -zs <strategies>	zlib compression strategies (0-3)	default 0-3
    -zw <window size>	zlib window size (32k,16k,8k,4k,2k,1k,512)
    -f  <filters>	PNG delta filters (0-5)			default 0,5
    -nb			no bit depth reduction
    -nc			no color type reduction
    -no			no output (simulation mode)
    -np			no palette reduction
    -nz			no IDAT recompression (also disable reductions)
    -fix		enable error recovery
    -force		write a new output even if it is larger than the input
    -preserve		preserve file attributes if possible
    --			stop option switch parsing
Optimization level presets:
    -o0  <=>  -nz
    -o1  <=>  [apply libpng heuristics]		(1 trial)
    -o2  <=>  -zc9 -zm8 -zs0-3 -f0,5		(8 trials)
    -o3  <=>  -zc9 -zm8-9 -zs0-3 -f0,5		(16 trials)
    -o4  <=>  -zc9 -zm8 -zs0-3 -f0-5		(24 trials)
    -o5  <=>  -zc9 -zm8-9 -zs0-3 -f0-5		(48 trials)
    -o6  <=>  -zc1-9 -zm8 -zs0-3 -f0-5		(120 trials)
    -o7  <=>  -zc1-9 -zm8-9 -zs0-3 -f0-5	(240 trials)
Examples:
    optipng -o5 file.png			(moderately slow)
    optipng -o7 file.png			(very slow)
    optipng -i1 -zc4,9 -zs0-2 -f0-2,4-5 file1.png file2.png
Notes:
  - The options are cummulative; e.g.
    -f0 -f5  <=>  -f0,5
    -zs0 -zs1 -zs2  <=>  -zs0,1,2  <=>  -zs0-2
  - The option letters are case-insensitive.
  - The libpng heuristics consist of:
    -o1  <=>  -zc9 -zm8 -zs0 -f0		(if PLTE is present)
    -o1  <=>  -zc9 -zm8 -zs1 -f5		(if PLTE is not present)
  - The zlib window size is set to a minimum that does not affect
    the compression ratio.
  - The output file will have all IDAT in a single chunk, even if
    no recompression is performed.
  - The most exhaustive search  -zc1-9 -zm1-9 -zs0-3 -f0-5  (1080 trials)
    is offered only as an advanced option, and it is not recommended.