Bash shell script-turned-Mac-service for batch processing using Guetzli
The script and service assume that Guetzli was installed with Homebrew via brew install guetzli which by default installs it into the path /usr/local/Cellar/guetzli/1.0/bin/guetzli. If you unarchived into another location, substitute that location in the script/service instead.
On Mac, GZLI_Default.workflow is seen as a "file" (though it is a folder structure, just like Mac .app files) that can be opened/edited in Automator or installed into Services. You can enable/disable services and mess around with them in Mac > Preferences > Keyboard > Shortcuts > Services
This is a very easy, simple script that can be heavily modified and has many uses. This can also be used to great effect with ImageMagick, and I recommend it for batch image workflows
Since it is such simple/generic code, it may already exist out there somewhere in a similar form.
Usage: To use, download this repository and in the release folder, when opened on Mac, the .workflow file will be available, double-click to install and/or open with Automator for further editing. When it installs this way, it installs by default to /Users/username/Library/Services
License: None / Open / Do-whatever-you-want-with-it
Disclaimer: The user assumes all responsibility for use of these files