I often make png images (mainly for this site) and one helpful tool to compress them is pngcrush.

I'm quite comfortable on the command line, but I thought there must be an easy way to do what I want just by right clicking.

Nemo (the file browser for the Cinnamon desktop environment) supports this easily.

Simply create a new action file. My example is called "pngcrush.nemo_action" and is created in user specific .local folder - mine being /home/dan/.local/share/nemo/actions.

You can click on More Info to show some documentation.

The content of this file is:

[Nemo Action]
Active=true
Name=Compress PNG
Comment=Compress PNG
Dependencies=pngcrush
Selection=notnone
Quote=double
Exec=<pngcrush.sh %F>
Icon-Name=gtk-execute
Extensions=png;

Key configurations here:

• Dependencies=pngcrush - means it won't show unless pngcrush is installed (done through Software Manager, or sudo apt install pngcrush)
• Selection=notnone - means the action won't show up when right clicking, but it will show if one or more files are selected
• Quote=double - escapes file names with spaces.
• Extensions=png; - this means the action will only show on png files. If at least one selection is not a png file, the action won't show.
• Icon-Name=gtk-execute - just gives a gear icon
• Exec=<pngcrush.sh %F> - finally, this says what script to run. The %F parameter means "insert path list of selection"

The script itself is a bash script that loops through the list of files sent and executes the command. The file named pngcrush.sh should also be created in the same folder ~/.local/share/nemo/actions. It also needs to be made executable (change via right click properties, or run a terminal in the actions directory and type chmod +x pngcrush.sh):

Here is the content of the sh file:

#!/bin/bash
for i in "$@"; do
    if [ -x "$i" ]; then
        continue
    fi
    pngcrush -brute "$i" "${i%%.*}_crushed.png"
done

The loop expands the input parameter to each file, into an i variable. To get the filename without the extension, greedy parameter expansion is used (the ${i%%.*} bit)

In the examples of this blog, this brought the screenshots from 104.4KB to 75.1KB - saving approximately 25% bandwidth. This helps more on larger articles/blogs and images.