Title: Port of the week: pngquant
       Author: Solène
       Date: 07 September 2021
       Tags: graphics unix portoftheweek
       Description: 
       
       # Introduction
       
       Today as a "Port of the Week" article (that isn't published every week
       now but who cares) I would like to present you pngquant.
       
       pngquant is a simple utility to compress png files in order to reduce
       them, with the goal of not altering the file in a visible way. 
       pngquant is lossy which mean it modify the content, at the opposite of
       the optipng program which optimize the png file to try to reduce its
       size as possible without modifying the visual.
       
 (HTM) pngquant project website
       
       # How to use
       
       The easiest way to use pngquant is simply give the file to compress as
       an argument, a new file with the original file name with "-fs8" added
       before the file extension will be created.
       
       ```shell commands
       $ pngquant file.png
       $ test -f file-fs8.png && echo true
       true
       ```
       
       # Performance
       
       I made a simple screenshot of four terminals on my computer, I compared
       the file size of the original png, the png optimized with optipng and
       the compressed png using pngquant.  I also included a conversion to jpg
       of the same size as the original file.
       
       I used defaults of each commands.
       
       ```table with results
       File                size (in kilobytes)        % of original (lower is better)
       ========        ===============                ===============================
       original        168                        100
       optipng                144                        85.7
       pngquant        50.2                        29.9
       jpeg 71%        169                        100
       ```
       
       The file produced by pngquant is less than a third of the original. 
       Here are the files so you can try to check if you see differences with
       the pngquant version.
       
       * Original file
 (IMG) Original file
       * Optimized file
 (IMG) Optimized file using optipng
       * Compressed file
 (IMG) Compressed file using pngquant
       * Jpeg conversion (targeting same size)
 (IMG) Jpeg file converted with ImageMagick
       
       # Conclusion
       
       Most of the time, compressing a png is suitable for publishing or
       sharing.  For screenshots or digital pictures, jpg format is usually
       very bad and is only suitable for camera pictures.
       
       For a drawn picture you should keep the original if you ever plan to
       make changes on it.