Hi!
ImageMagick at the command line for linux and little bit later for windows exist since the beginning of the 90s.
The package is called ImageMagick.
On the command line you call it with
magick and a lot of parameters.
But there are a lot of commands more like
animate, composite and
montage.
See the "Tools" page at
https://imagemagick.orgOn Suse and on Apple it is included in the standard instalation.
One reason to put magick into a shell script is the horrible amount of possible parameters. So you can write a script for your special needs.
The other reason is doing some loop stuff for great quantity of images. "Please help me to downsize these 600 photos for the web" - asked me a friend. She owns a Graphic Studio. 5 Minutes searching the terminal on an Apple (unknown OS!), 10 minutes writing a script including magick. Then you can go smoking. While the computer works.
The pascal interface came a lot of time later than the command line version - I think.
Winni