Title: Port of the week: pngquant

	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.

	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
	Original file
	* Optimized file
	Optimized file using optipng
	* Compressed file
	Compressed file using pngquant
	* Jpeg conversion (targeting same size)
	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.