| 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.
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# 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 |
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# 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. |
