How to optimize png format image in command line mode? The answer is Optipng ,Optipng is a simple and useful tool for optimizing png image runs in command line mode.

Installation:

Optipng has been added to most of Linux distroes’ repositories,so install it is very easy :~

Debian/Ubuntu：$ sudo apt-get install optipng
Fedora：# yum install optipng
Archlinux：# pacman -S optipng
Opensuse: YAST->SoftwareManage ,seach “Optipng” and select it.

Example:

I have a png  image names optipng.png  in  my home folder,i  can use below command to optimize it:

$optipng optipng.png

after I optimized the optipng.png,its size turn to 9Kb from 20.2Kb and the image quality is still very good!

optipng1

Usage( easy:) )

optipng [options] files …
Files:
Image files of type: PNG, BMP, GIF, PNM or TIFF
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 modified files
-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
-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
-full produce a full report on IDAT (might reduce speed)
-preserve preserve file attributes if possible
-simulate run in simulation mode, do not create output files
-out <file> write output file to <file>
-dir <directory> write output file(s) to <directory>
-log <file> log messages to <file>
– 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)
Notes:
- The option names are case-insensitive and can be abbreviated.
- Range arguments are cumulative; e.g.
-f0 -f3-5 <=> -f0,3-5
-zs0 -zs1 -zs2-3 <=> -zs0,1,2,3 <=> -zs0-3
- 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 most exhaustive search -zc1-9 -zm1-9 -zs0-3 -f0-5 (1080 trials)
is offered only as an advanced option, and it is not recomended.
You may implement “man optipng” to see more Optipng’s parameters.