PNGquant is one of best tool for lossy compression of PNG images. Its reduce the PNG image size upto 70% and maintain full alpha transparency.

Easy to convert large number of images,

Easy to integrate server side with shell script

Default pngquant installation path is, /usr/local/bin/pngquant

download  and Installation:

# wget http://pngquant.org/pngquant-2.4.0-src.tar.bz2

# cd pngquant-2.4.0

# ./configure --with-openmp --with-lcms2


 Compiler: gcc

     Debug: no

       SSE: yes

    OpenMP: yes

    libpng: shared (1.2.49)

      zlib: shared (1.2.3)

     lcms2: error ... not found (please install libcms2-devel package)


Error :lcms2-devel packages could not found it just following below steps,

Solution:

 Download the latest epel-release rpm from

http://dl.fedoraproject.org/pub/epel/6/x86_64/

Install epel-release rpm:
 
# rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

Install lcms2-devel rpm package:
 
# yum install lcms2-devel -y

Then try again,

#  ./configure --with-openmp --with-lcms2


 Compiler: gcc

     Debug: no

       SSE: yes

    OpenMP: yes

    libpng: shared (1.2.49)

      zlib: shared (1.2.3)

     lcms2: shared (2.3)


To find the version:
 
# pngquant --version
2.4.0 (March 2015)

 
# pngquant --help

How to Use pngquant?

For example convert a .png file format, just see the image file size,before conversion,
 
# du -sch thelinuxfaq_pngquant.png
40K     thelinuxfaq_pngquant.png

 
# pngquant  -ext .png --force yourimage.png

Aftet conversion,
 
# du -sch thelinuxfaq_pngquant.png
22K     thelinuxfaq_pngquant.png


Also, can convert with quality based,
 
# pngquant  -ext .png --quality 30-50 --force yourimage.png


 --force                 overwrite existing output files (synonym: -f)

 --ext new.png        set custom suffix/extension for output filenames

 --quality min-max    don't save below min, use fewer colors below max (0-100)


Before conversion file size,
 
# du -sch /home/thelinuxfaq/png-images


88K     linuxfaq.png

88K     thelinux_faq.png

88K     the_linux.png
# find . -name '*.png' -exec pngquant -ext .png -force 256 {} \;

After conversion files size,
 
# du -sch *


40K     linuxfaq.png

40K     thelinux_faq.png

40K     the_linux.png


How to use for PHP:

The below sample code for conversion with exec


<?php

 echo $get_compress = exec("find /image/source/path -name '*.png' -exec /usr/local/bin/pngquant -ext .png -force 256 {} \;");

?>